OPINION OF THE COURT
GARTH, Circuit Judge.Defendant Stephen Gibbs was convicted after a jury trial in the United States District Court for the Eastern District of Pennsylvania of conspiracy to distribute marijuana in violation of 21 U.S.C. § 846 (1976). The conviction was based primarily on statements made by a co-conspirator, Joseph Quintiliano, that were admitted into evidence against Gibbs under Fed.R.Evid. 801(d)(2)(E), which creates a category of non-hearsay for co-conspirators’ admissions.
On appeal to a panel of this court, Gibbs argued that (1) the prerequisites for the admission into evidence of co-conspirator testimony were not satisfied, and that (2) the introduction of that evidence violated his sixth amendment right to confront and cross-examine the witnesses against him. We hold that the challenged testimony was *840properly admitted under Fed.R.Evid. 801(d)(2)(E) and we also hold that Gibbs' sixth amendment confrontation issue was not adequately preserved for appeal. Thus, we affirm the judgment of conviction entered below.
I.
Stephen Gibbs was one of six persons indicted for conspiracy to violate federal narcotics laws.1 At his trial, Gibbs did not dispute that in 1980 Joseph Quintiliano and several others participated in a conspiracy to import marijuana into the United States with the intent to distribute it for sale. Rather, Gibbs’ defense was that there was insufficient evidence of his own participation in the conspiracy.
The existence of the conspiracy was firmly established at trial. The evidence showed that early in 1980, Quintiliano began to make plans to import marijuana into Pennsylvania from Colombia, South America. In late March, he purchased a Beech-craft twin-engine airplane for $40,000. According to the testimony of two unindicted co-conspirators, Charles Bilella and David White,2 Quintiliano stated on several occasions in late March and early April that he intended to use the airplane to transport marijuana from Colombia into Pennsylvania. From April to September 1980, Quintiliano and the other conspirators made efforts to repair and equip the plane for smuggling. In late September, after several test flights, pilot Prentiss Breland3 flew the plane from Pennsylvania to Homestead, Florida. On October 4, Breland flew the plane from Florida to Colombia. Upon his return trip to Pennsylvania in the early morning- hours of October 5, Breland missed a planned refueling stop in the Bahamas and was forced to land at Boca Raton, Florida, to refuel. A few hours later Breland was arrested at the Florida airport and the plane, containing marijuana worth over $400,000, was seized.4
The Government prosecutéd Gibbs on the theory that he participated in the conspiracy as the intended purchaser of the marijuana. The evidence linking Gibbs to the conspiracy fell into three categories. First, the Government established that on April 7, 1980, Gibbs traveled from his home in Massachusetts to Quakertown, Pennsylvania, for a meeting with Quintiliano. Gibbs flew to Philadelphia and was met there by David White, who then flew him to meet Quintiliano at Wings Airfield in Montgomery County, Pennsylvania. Surveillance officers testified that Quintiliano greeted Gibbs at Wings Airfield and drove him to the Perkins Pancake House, the site of other conspiracy meetings, where they conversed privately. Quintiliano and Gibbs then proceeded to Quakertown Airport where the Beechcraft was located, and together they inspected the airplane for several minutes. Upon leaving the airport, they were followed by Pennsylvania state *841troopers who observed that the people in the vehicle (Quintiliano and Gibbs) were looking around to see if someone was following them and that Quintiliano engaged in several driving maneuvers that the officers testified were designed to evade surveillance, i.e., a brief pull-off into a hotel area, followed by a resumption of travel in the same direction, and then, after further “looks” by the driver and passenger, a U-turn to proceed in the direction from which they had come.
The second category of evidence upon which the Government relied, and in fact the principal evidence offered against Gibbs, was derived from statements made by Quintiliano that implicated Gibbs in the conspiracy. Bilella and White testified that in the spring of 1980, around the time Quintiliano purchased the Beechcraft and began to repair it, Quintiliano stated that he planned to sell the marijuana to a customer named “Jake” with whom he had dealt before. On April 6, 1980, the day before Gibbs’ visit to the Quakertown airport, Quintiliano told White that “Jake” was growing impatient with the slow progress of the planning, and that Quintiliano had invited “Jake” to come for a visit the next day (i.e., April 7, 1980) to see firsthand the preparations for the Colombia trip. White volunteered to meet “Jake” at the Philadelphia airport and to take him to Wings Airfield to meet with Quintiliano. White testified that the following day he went to Philadelphia and met defendant Gibbs, who identified himself as “Jake” and matched the description of “Jake” given by Quintiliano. Gibbs told White that he had been informed of the arrangements for White to meet him in Philadelphia.
Bilella also testified to an out-of-court statement by Quintiliano. According to Bilella, sometime during the first week in October, Quintiliano told him that he had made arrangements to sell the marijuana to some people from Florida who had offered more money than “Jake.” (Gibbs argues that this testimony indicates that he, Gibbs, had dropped out of the conspiracy.)
White and Bilella also testified to a series of events that took place at Quintiliano’s home on the evening of October 4, 1980, including statements by Quintiliano concerning telephone conversations that incriminated Gibbs in the conspiracy. Bilella testified that while he was in Quintiliano’s home early that evening, he heard Rizo and Quintiliano discussing financial arrangements for the sale of the marijuana to the people from Florida, who were staying nearby. Quintiliano apparently became dissatisfied with these terms because the prospective buyers were unable to pay cash in advance. Quintiliano stated that he had telephoned “Jake” to see if he would buy the marijuana, and that “Jake” had agreed to “try to make the necessary arrangements.” 5
White testified that while at his own home that evening, he received a telephone call from Quintiliano asking him to come to Quintiliano’s residence. When White arrived about 10:45 p.m., Quintiliano apprised him of the developments earlier in the evening. Quintiliano described to White three telephone conversations he had had with his Miami bosses, who had instructed Quintiliano not to distribute the marijuana without receiving full payment.6 White also testified regarding Quintiliano’s account of a telephone call to “Jake” in which “Jake” reportedly had agreed to buy the marijuana but needed timé to obtain the necessary *842funds.7 These conversations between White and Quintiliano took place in Rizo’s presence. White further testified that he heard Quintiliano instruct his brother Jerry to call “Jake” from a pay phone. Quintiliano asked White for permission to store the marijuana temporarily in his shop until “Jake” could get the money, and at about 12:30 a.m. on October 5, 1980, White, Quintiliano, and other conspirators met at White’s shop to clear storage space for the marijuana.
The third category of evidence by which the Government sought to link Gibbs to the conspiracy and to corroborate the co-conspirator testimony consisted of telephone records showing long distance calls made from the Quintiliano residence in Pennsylvania. At least six telephone calls were made from Quintiliano’s residence to the Gibbs residence in Massachusetts between March and May 1980.8 Four such calls were made during September 1980, three of which occurred on September 26-27, about the time Breland flew the plane to Florida. Another call was made on October 3, 1980, the day before the plane left for Colombia. In addition, two calls were made from the Quintiliano residence to the Gibbs residence in the early morning hours of October 5, at the time the plane was due in Quakertown. The second such call, made at 3:39 a.m., followed a call from Quintiliano to David White, who was waiting at Quakertown Airport, in which Quintiliano told White that something had gone wrong with Breland’s flight home.
There also was evidence of telephone calls on October 4, 1980, from Quintiliano’s residence to the Ram Broadcast Co. (Ram), an electronic beeper service located near Gibbs’ home in Massachusetts.9 Although there was no direct evidence that the defendant was a client of Ram, the Government did demonstrate that one of Ram’s customers was a “Gibbs Oil Co.” and that Gibbs himself had claimed to be involved in the oil business. There was no evidence that these calls to Ram were returned.
On appeal, Gibbs contends that the district court erred in allowing the jury to consider the statements made by Quintiliano to White and Bilella as evidence against Gibbs. He maintains that Quintiliano’s out-of-court statements were hearsay declarations that should have been excluded from admission under the Federal Rules of Evidence and under the Confrontation Clause of the sixth amendment to the Constitution.
II.
Under the Federal Rules of Evidence, the out-of-court statements of a party to the case or of his agent are considered “admissions” — non-hearsay10—and may be used as substantive evidence. See Fed.R.Evid. 801(d)(2). Rule 801(d)(2)(E) provides that statements offered against a party that are made “by a co-conspirator of a party during the course and in furtherance of the conspiracy” are not hearsay and are admissible. In this case, the district court found *843that Quintiliano’s out-of-court statements were admissible against Gibbs as co-conspirator admissions.
Before an out-of-court statement can be admitted into evidence under Fed.R. Evid. 801(d)(2)(E), three requirements must be satisfied. United States v. Ammar, 714 F.2d 238, 245 (3d cir.), cert. denied, — U.S. -, 104 S.Ct. 344, 78 L.Ed.2d 311 (1983). First, there must be independent evidence establishing that the person against whom the statement is offered participated in the conspiracy. Second, the statement must have been in furtherance of the conspiracy. - Third, the co-conspirator’s statement must have been made during the life of the conspiracy. Gibbs contends that the first and second prerequisites are not met in this case.
A. Independent Evidence of Conspiracy
According to the rule of United States v. Trotter, 529 F.2d 806 (3d Cir. 1976), the prosecution must lay a foundation for the admission of co-conspirator testimony by establishing the existence of a conspiracy including the defendant by “a fair preponderance of independent evidence.” Id. at 811-13. See Ammar, 714 F.2d at 246 & n. 3.; Government of the Virgin Islands v. Dowling, 633 F.2d 660, 665 (3d Cir.), cert. denied, 449 U.S. 960, 101 S.Ct. 374, 66 L.Ed.2d 228 (1980); United States v. Continental Group, Inc., 603 F.2d 444, 457 (3d Cir.1979), cert. denied, 444 U.S. 1032, 100 S.Ct. 703, 62 L.Ed.2d 668 (1980).11 .This preponderance standard simply requires the prosecution to present sufficient proof so that the trial judge may find “that the existence of the contested fact is more probable than its nonexistence.” Trotter, supra, 529 F.2d at 812 n. 8 (quoting McCormick, Evidence 794 (2d ed. 1972)).12 In reviewing the district court’s determination that a preponderance of independent evidence established Gibbs’ participation in the conspiracy, this court’s inquiry is limited to whether the trial judge had “reasonable grounds” to make his finding. Ammar, 714 F.2d at 249; Continental Group, 603 F.2d at 460; United States v. Bey, 437 F.2d 188, 196 (3d Cir.1971).
In holding that the district court did not err in finding that the conspiracy existed and that Gibbs participated in the conspiracy we do not consider the alleged telephone conversations between Quintiliano and Gibbs to which White and Bilella testified.13 The existence of a conspiracy in this case is clear and uncoritested. As for Gibbs’ participation in the conspiracy, the independent evidence (i.e., evidence apart from the testimony of White and Bilella) offered by the Government to prove that Gibbs was a member of the conspiracy, while not weighty, was nevertheless sufficient. The Government relied heavily on Gibbs’ visit to Pennsylvania in April 1980 and on telephone records showing calls made from Quintiliano’s residence to Gibbs’ residence or Ram Broadcast Co. around the time of the unsuccessful smuggling operation.
*844The circumstances surrounding Gibbs’ April 7, 1980, visit to see Quintiliano, the principal conspirator, provides some evidence that Gibbs was involved in Quintiliano’s scheme at that time. The meeting took place only nine days after Quintiliano bought an airplane to be used for smuggling marijuana into the United States, and it took Gibbs a considerable distance from home to the place of the conspiratorial planning. Gibbs and Quintiliano had obviously had some communication prior to the visit. Although the plane was located at Quakertown Airport, White was instructed by Quintiliano to take Gibbs to Wings Airfield,14 from which the Government suggests an inference can be drawn that Gibbs and Quintiliano wanted to hide their connection with the smuggling plane located at Quakertown Airport.15 Gibbs and Quintiliano conferred at the Perkins Pancake House, the site of previous conversations between Quintiliano and White and Bilella concerning the conspiracy. The defendant and Quintiliano then proceeded to Quaker-town Airport, where they inspected the plane to be used in the smuggling operation. Finally, evidence of Quintiliano’s evasive driving after leaving Quakertown Airport accompanied by his passenger Gibbs, and the frequent glances by both Quintiliano and Gibbs for the apparent purpose of detecting surveillance allows the further inference of unlawful activity. See United States v. D'Amato, 493 F.2d 359, 364-65 (2d Cir.), cert. denied, 419 U.S. 826, 95 S.Ct. 43, 42 L.Ed.2d 50 (1974) (counter-surveillance driving indicative of conspiracy).
We recognize that at that point in the trial the evidence of Gibbs’ contacts with Quintiliano may have fallen short of establishing Gibbs’ involvement in the conspiracy beyond a reasonable doubt. But that is not the appropriate standard to be applied at that stage. The evidence, as recounted above, permits a reasonable inference of Gibbs’ complicity in the enterprise then under way. Wé cannot say that the district court lacked reasonable grounds to infer that Gibbs was participating in the conspiracy at the time of his visit.16
Because most of the co-conspirator declarations offered by the Government were made six months after Gibbs’ April 7, 1980, visit to Pennsylvania, we must consider whether there was sufficient independent evidence from which the district court reasonably could have inferred that Gibbs was still involved in the conspiracy in October 1980. The Government, in seeking to demonstrate the necessary predicate for admission of Quintiliano’s co-conspirator declarations, relied on a presumption that Gibbs’ membership in the conspiracy continued until October 1980.17
*845This court has held that once the Government establishes a defendant’s involvement in an ongoing conspiracy, the burden shifts to the defendant to prove by affirmative acts inconsistent with the object of the conspiracy that he withdrew.18 Ammar, 714 F.2d at 254; United States v. Steele, 685 F.2d 793, 803-04 (3d Cir.1982), cert. denied, 459 U.S. 908, 103 S.Ct. 213, 74 L.Ed.2d 170-(1983); United States v. Gillen, 599 F.2d 541, 548 (3d Cir.), cert. denied, 444 U.S. 866, 100 S.Ct. 137, 62 L.Ed.2d 89 (1979).19 Because there is no evidence that Gibbs withdrew from the conspiracy after April, his involvement may be deemed to have continued until October,20 making him a conspirator at the time of Quintiliano’s incriminating statements to White and Bilella on October 4 and 5, 1980. Therefore, we conclude that the district court did not err in its determination that the Government met its burden of establishing by a preponderance of independent evidence that Gibbs was involved in the conspiracy at the time of Quintiliano’s statements.
B. “In Furtherance” of the Conspiracy
Gibbs argues that the Government did not satisfy the requirement of Fed.R.Evid. 801(d)(2)(E) that the statements be made in furtherance of the conspiracy. Gibbs claims that Quintiliano’s statements to White and Bilella were mere “narratives of past fact” and not made to induce conduct that would further the goals of the conspiracy, and that White and Bilella were mere “errand runners.”
Gibbs’ argument is meritless. The “in furtherance” requirement is usually given a broad interpretation. See United States v. Trotter, supra, 529 F.2d at 813. It is true that statements made to those who are not involved in the conspiracy are not “in furtherance” of it, United States v. Provenzano, 620 F.2d 985, 1000-01 (3d Cir.), cert. denied, 449 U.S. 899, 101 S.Ct. 267, 66 L.Ed.2d 129 (1980), just, as casual conversation between co-conspirators that is not intended to induce continued involvement, or other actions that would not advance the conspiracy, are not “in furtherance” of a conspiracy. See, e.g., United States v. Lieberman, 637 F.2d 95, 103 (2d Cir.1980); United States v. Eubanks, 591 F.2d 513, 520-21 (9th Cir.1979). But statements made by one conspirator to keep other conspirators informed about the progress of the scheme do satisfy the “in furtherance” requirement. See, e.g., Ammar, 714 F.2d at 252; United States v. Pool, 660 F.2d 547, 562 (5th Cir.1981); *846United States v. Mason, 658 F.2d 1263, 1270 (9th Cir.1981).
In the present case, there was a reasonable basis for the trial court to find that Quintiliano’s statements to Bilella and White were made in furtherance of the conspiracy. As participants in the scheme, it was important for White and Bilella to be kept abreast of developments to induce their continued participation and allay any fear they might have had. Although neither White nor Bilella had any decision-making role or any real interest in the identity of the buyer, they both had been closely involved in the planning and implementation of the conspiracy. White had picked up Gibbs at the Philadelphia Airport and brought him to the conference rendezvous with Quintiliano in April, and had also agreed to help unload the marijuana when the plane arrived. Quintiliano, who specifically had asked White to come to his home for a talk, may have foreseen that he would be requesting White’s cooperation in storing the marijuana temporarily. Although Bilella at that time had no specific duties with respect to the conspiracy, he had repeatedly rendered assistance to Quintiliano; he had at Quintiliano’s request found the Béechcraft plane for purchase and had introduced him to White, an experienced pilot. Quintiliano also may have felt that he would need Bilella’s help in the future. Under these circumstances, Quintiliano’s reports to White and Bilella did further the conspratorial scheme.
This case is distinguishable from United States v. Provenzano, supra, where the co-conspirator’s statements were held not to be in furtherance of the conspiracy. Contrary to the circumstances of the instant case where all the statements were made to co-conspirators, in Provenzano, the statements were made to persons not part of the conspiracy who had no reason to know about the matters disclosed to them.
We conclude that the Government satisfied its burden of laying the necessary foundation for admission of Quintiliano’s co-conspirator statements against Gibbs under Fed.R.Evid. 801(d)(2)(E). It remains for us to consider Gibbs’ contention that his constitutional rights under the sixth amendment Confrontation Clause were violated.
III.
The sixth amendment guarantees that “[i]n all criminal prosecutions, the accused shall enjoy the right ... to be confronted with the witnesses against him.” Gibbs contends on appeal that the admission of out-of-court statements made by Quintiliano on October 4 and. 5, 1980, had the effect of denying Gibbs his constitutional right to confront and cross-examine his accuser. Gibbs argues that under the rule of Ohio v. Roberts, 448 U.S. 56, 65-66, 100 S.Ct. 2531, 2538-39, 65 L.Ed.2d 597 (1980), which examined the bounds of the sixth amendment, the Government was required to prove that the declarant, Quintiliano, was unavailable, and that the co-conspirator evidence was reliable,21 before any such testimony could be admitted into evidence. *847We recognize that no exact equation exists between Fed.R.Evid. 801 and the Confrontation Clause, see Dutton v. Evans, 400 U.S. 74, 86, 91 S.Ct. 210, 218, 27 L.Ed.2d 213 (1970); Ammar, 714 F.2d at 254-55, thereby raising the possibility that evidence that satisfies Fed.R.Evid. 801(d)(2)(E) could still be deemed inadmissible under the constitutional test. Gibbs has argued that unavailability must be demonstrated and that the Government has the burden of establishing unavailability. However, we have no occasion to discuss or to reach, the merits of that issue in this case, i.e., whether unavailability must be shown to satisfy the Confrontation Clause where a co-conspirator statement is sought to be admitted. Even if we were to assume that unavailability had to be demonstrated, Gibbs did not preserve that question for appeal.
The Confrontation Clause issue now raised by Gibbs — i.e., that the Government did not carry its burden of proof as to unavailability and reliability of the evidence (see note 21 supra) — was never raised by Gibbs during trial. Had Gibbs, by a specific objection, timely made, alerted the Government and the district court to the fact that no proof of unavailability had been presented by the Government, that deficiency could have been cured. But because Gibbs did not preserve that issue for appeal, it cannot serve now as a basis to reverse Gibbs’ conviction.
A.
The evidence against Gibbs, the ostensible purchaser in a conspiracy to import and distribute a large quantity of marijuana, consisted in significant part of the testimony of Bilella and White, two unindicted co-conspirators, who testified to a number of hearsay declarations by Quintiliano (the alleged chief conspirator, .who did not testify at trial) to the effect that Quintiliano planned to sell the marijuana to a customer named “Jake” (Gibbs).
At no time during the Government’s case-in-chief, however, did Gibbs object to any of Quintiliano’s hearsay declarations on Confrontation Clause grounds. Rather, Gibbs’ counsel asserted that under the co-conspirator rule, Fed.R.Evid. 801(d)(2)(E), Quintiliano’s out-of-court declarations were inadmissible because the Government had not established, by independent evidence, either the existence of a conspiracy or Gibbs’ involvement in the conspiracy. During White’s testimony, for example, the following exchange transpired:
Q. Mr. White, did Joseph Quintiliano ever mention to you potential buyers for the marijuana?
MR. BERGSTROM: Objection.
It is hearsay, Your Honor, and there is no proof aliunde of a conspiracy at this point in the case.
THE COURT: Well, that we do not find persuasive.
We will permit the question.
App. at 43a. Counsel later obtained a standing objection to White’s repetition of Quintiliano’s out-of-court declarations. Id. at 55a.
Similarly, during Bilella’s testimony the following exchange took place:
Q. Now, you mentioned someone by the name of “Jake.” •
Who was it that told you about “Jake”?
A. Well, Joe had mentioned a fellow named—
MR. BERGSTROM: Objection — it is hearsay, Your Honor, for the record, sir.
THE COURT: Your response, Mr. Huyett.
MR. HUYETT: Yes, sir.
It is a co-conspirator statement.
THE COURT: Yes.
The witness may [answer] the question if he understands it.
App. 248a.
At this juncture, Gibbs did not question, and consequently the Government had no obligation to answer, whether the introduction of Quintiliano’s declarations would violate the Confrontation Clause — much less that the Confrontation Clause would require a showing of unavailability. Thus, it is not surprising that the question of who bore the burden of establishing Quintili*848ario’s unavailability, and the concomitant factual question as to whether Quintiliano was unavailable, never arose. Certainly Gibbs never raised any such issue. And because Rule 801 22 — unlike Fed.R.Evid. 80423 — does not require a showing of unavailability, the subject of Quintiliano’s availability never became an issue, and thus never'became part of the record.
On November 27, 1981, the Government rested. App. 442a. Gibbs then moved, pursuant to Fed.R.Crim.P. 29(a), for a judgment of acquittal. At the same time, counsel for Gibbs stated that “it would probably be necessary for me also to make a motion to the Court to ... strike all of the hearsay co-conspirator declarations from the record.” App. 448a. Gibbs renewed at this stage the argument, raised in his Memorandum of Law and by his trial objections referring to Fed.R.Evid. 801, that the Government failed to establish “a conspiracy by a clear preponderance of the evidence independent of the co-conspirator statement and the participation of the defendant, Gibbs, in that conspiracy ____” Id.
In addition, for the first time Gibbs observed “yet ¿nother problem.” App. 452a. “Aside from [Rule] 801(d)(2)(E),” Gibbs argued, “there is a clear Sixth Amendment problem in this case.” Id. Noting that the co-conspirator hearsay rule “does not subsume and take the place of the Sixth Amendment right to confrontation,” Gibbs asserted that the “Sixth Amendment right and Rule 801(d)(2) are going to come smashing head on into one another ... in this case.” Id. at 452a-53a. The essence of Gibbs’ sixth amendment objection is captured by the following passage:
The [men] who should have been on that witness stand and whom I should have been able to cross-examine [were] Joe Quintiliano [and his brother] Jerry Quintiliano, the declarant[s] of the hearsay statements], and I have been denied through this case the right to confront and cross-examin[e] [those] who really are the ultimate accusers in this case ... —that being Joseph and Jerry Quintiliano.
App. 453a.
At no time during these remarks, however, did Gibbs assert that Quintiliano was in fact available, or that the Government had the burden of showing unavailability and had not carried this burden. As a consequence, neither the Government nor the district court was alerted to the nature of the issue upon which Gibbs now seeks to have his conviction reversed.
Had anyone mentioned the word “availability,” of course, it would have been a relatively simple matter for the Government to address that question and produce proofs as to Quintiliano’s availability or unavailability. Presumably the Government could have called Quintiliano, and if Quintiliano had asserted the fifth amendment privilege against self-incrimination, he then would have been deemed unavailable. See United States v. Pelton, 578 F.2d 701, 709-10 (8th Cir.1978). Hence, it is solely by reason of Gibbs’ failure to raise the issue of Quintiliano’s availability before the district court,' that the record is barren of any evidence of Quintiliano’s unavailability.
The district court denied Gibbs’ motion to strike and motion for judgment of acquittal without comment on Gibbs’ general constitutional objection. The court found only that “the Government has established the existence of an alleged conspiracy and the connection of each defendant with it by a clear preponderance of the evidence independent of the hearsay declarations.” App. at 480a. The defense rested immedi*849ately thereafter. • Gibbs’ conviction followed.
B.
There are compelling reasons why Gibbs’ Confrontation Clause objection— even if it had been specifically made, and even if it had addressed the issues of burden of proof and unavailability, which it did not — should be regarded as untimely.
First, Fed.R.Evid. i03(a)(l) requires that a timely objection or motion to strike must “stat[e] the specific ground of objection, if the specific ground was not apparent from the context.” Gibbs can hardly argue that the issue of the Government’s failure to establish Quintiliano’s unavailability — an argument that eluded the Government and the district court — was “apparent from the context.” It follows that Gibbs was obliged to satisfy the specificity requirement of Rule 103.
The Advisory Committee Notes to Rule 103 indicate that the purpose of the specificity requirement is to call the nature of the error “to the attention of the judge, so as to alert him to the proper course of action and enable opposing counsel to take proper corrective measures.” Rule 103(a) Advisory Comm. Note. Gibbs’ objection is the model of an objection that fails the Advisory Committee’s test. At no time was the district court ever apprised that the nub of Gibbs’ complaint was that the Government had not proved Quintiliano’s unavailability. As a consequence, the Government was deprived of the opportunity to take corrective measures — including the possibility of calling Quintiliano in order to establish that he would assert the fifth amendment privilege.
Second, even assuming that Gibbs’ objection was sufficiently specific, Gibbs made his constitutional objection not when the evidence was offered, but during a motion to strike made after the Government rested. As a consequence, the many co-conspirator declarations related by White and Bilella over the course of a three-day trial were already in evidence.
As Professors Wright and Graham note, the appropriate time for raising an objection is as soon as the ground for objection is known, or could reasonably have been known to the objector — unless some special reason makes its postponement desirable and not unfair to the opposition. 21 C. Wright & K. Graham, Federal Practice and Procedure § 5037, at 188 (1977). Nothing prevented Gibbs’ counsel from raising an objection when White first testified. Gibbs could have objected to the following effect: “Your Honor, although Rule 801 does not require .that the declarant be unavailable, the Confrontation Clause does. Because there is no evidence that Quintiliano is unavailable, the evidence is inadmissible.”
This simple objection, if made when the Government sought to introduce the testimony of White and Bilella, would have warned the Government of the need to call Quintiliano, or to prove his unavailability in other ways. No special reasons made a postponement of this objection desirable, and a good many reasons made its postponement unfair. Not the least of these reasons is that the Government would have been obliged to reopen its case in order to establish Quintiliano’s unavailability — a matter which, from his silence at trial, we can only assume Gibbs had taken for granted.
If Quintiliano ultimately proved to be unavailable, a delay of several days might have resulted until the Government produced him — a delay that could have been obviated had Gibbs’ constitutional objection been made during the trial, when it would have been timely, rather than after the evidence had closed. Even at that late date, an issue raised as to unavailability could still have been met by the Government. If, however, Quintiliano had proved to be “available” — perhaps because he would choose not to assert his fifth amendment .privilege — Gibbs’ motion to strike, if granted, would almost certainly have been followed by a motion for mistrial on the ground that no jurors could be expected to expunge from their minds the many hearsay declarations adduced throughout three days of prior testimony.
*850This court has frequently held that it will not entertain arguments on appeal based on objections not timely raised below. See Halderman v. Pennhurst State School & Hospital, 673 F.2d 628, 639 (3d Cir.1982) (in banc), reversed on other grounds, — U.S. -, 104 S.Ct. 900, 79 L.Ed.2d 67 (1984); Caisson Corp. v. Ingersoll-Rand Co., 622 F.2d 672, 680 (3d Cir.1980). To do so here would constitute an unacceptable interference with the administration of justice and the district court’s management of the trial. We reverse the trial judge's determination of timeliness only for an abuse of discretion.24 The circumstances here do not rise to that level. For these reasons, we hold Gibbs’ objection untimely25 and insufficient to preserve a Confrontation Clause “unavailability” issue for appeal.
V.
As we have discussed, we are satisfied that there was sufficient evidence to withstand Gibbs’ 801(d)(2)(E) objection, which had been properly taken. Gibbs, however, did not preserve in timely fashion the Confrontation Clause issue which he has raised on appeal. His failure to alert the Government or the court to the issue of Quintiliano’s unavailability precludes our consideration of Gibbs’ argument which involves, among other things, the Government’s failure to carry its sixth amendment burden of proof. Having failed to preserve this issue at the threshold, there is no need for us to address the merits of his sixth amendment argument.
We will affirm Gibbs’ conviction.
. Also named in the indictment were Joseph Quintiliano (an alleged co-conspirator), Jerry Quintiliano (Joseph's brother), Prentiss Breland, Michael O’Looney, and Alejandro Rizo. All six defendants were charged in Count I of the indictment with conspiracy to distribute and to possess with the intent to distribute marijuana, in violation of 21 U.S.C. § 846. All of the defendants except Gibbs were also charged with conspiracy to import marijuana unlawfully, in violation of 21 U.S.C. § 963 (Count II) and with the substantive offense of illegal importation of marijuana in violation of 21 U.S.C. § 952 (Count III). Gibbs was tried jointly with codefendant Rizo, who was convicted on two counts of the indictment. The trial of Prentiss Breland was severed, and the other three defendants pleaded guilty to the indictment.
. Bilella was an aviation insurance broker and Quintiliano’s cousin. White, an experienced pilot, was introduced to Quintiliano by Bilella. Throughout the conspiracy, White acted as an informant for the Federal Drug Enforcement Administration (DEA).
. Prentiss Breland was convicted of violating 21 U.S.C. § 846 (conspiracy to possess with intent to distribute marijuana) and 21 U.S.C. § 963 (conspiracy to import marijuana) and he was sentenced to fifteen years imprisonment on the § 846 count and five years probation on the § 963 count. This court affirmed that judgment and conviction. United States v. Breland, 709 F.2d 1490 (3d Cir.1982).
. DEA Agents were notified by David White, who called from Pennsylvania to alert them that Breland had landed in Florida with drugs.
. Q: What did he [Quintiliano] say about "Jake” to you that evening?
A: He said he had called. He went to another room and said he had called up "Jake” and asked him if he could perhaps make arrangements to have someone come down and pick up this load.
Q: Did he tell you whether he had reached "Jake" to speak to him?
A: He had spoken to-him, yes.
Q: And did he tell you what "Jake's" response to him was?
A: That he would try to make the necessary arrangements, yes.
App. 273a (Bilella on Direct Examination).
. The telephone records show that Quintiliano made one call to Florida at 10:52 p.m.
. Q: Were other telephone calls made that evening?
A: Joe made a call to a — gentleman named “Jake” in — in the Boston or Massachusetts area to see if he would buy the — marijuana.
Q: And after that telephone call, what did Joe say about the call? '
A: Joe told me that “Jake” would buy the marijuana. He only could — could that night — he only had a hundred thousand dollars cash on hand. We — he would be able to get the rest of the money in a day or when the banks opened.
App. 109a (White on Direct Examination).
. The evidence documents five calls in March and one in May 1980. The Government offered no records for the month of April.
. The first such telephone call was made early in the morning of October 4. A call was also made that night at 8:52 p.m., and at 10:21 p.m., a call to Ram was placed from a pay telephone near Quintiliano's home and charged to the Quintiliano residence.
. Technically, the federal rules exclude admissions from the definition of hearsay rather than treating them as exceptions to the rule against hearsay. See United States v. Ammar, 714 F.2d 238, 255 (3d Cir.), cert. denied,-U.S.-, 104 S.Ct. 344, 78 L.Ed.2d 311 (1983). For simplicity, we will refer to the “co-conspirator exception.”
. Other courts have also adopted this rule. See, e.g., United States v. Andrews, 585 F.2d 961 (10th Cir.1978); United States v. Santiago, 582 F.2d 1128 (7th Cir.1978); United States v. Enright, 579 F.2d 980 (6th Cir.1978); United States v. Bell, 573 F.2d 1040 (8th Cir.1978); United States v. Stanchich, 550 F.2d 1294 (2d Cir.1977); United States v. Jones, 542 F.2d 186 (4th Cir.), cert. denied, 426 U.S. 922, 96 S.Ct. 2629, 49 L.Ed.2d 375, 376 (1976). But see United States v. Bulman, 667 F.2d 1374, 1377-79 (11th Cir.), cert. denied, 456 U.S. 1010, 102 S.Ct. 2305, 73 L.Ed.2d 1307 (1982) (adopting Fifth Circuit precedent of "substantial independent evidence" test); United States v. Slade, 627 F.2d 293, 307 (D.C.Cir.1980) (same test); United States v. James, 590 F.2d 575 (5th Cir.) (en banc) (same test), cert. denied, 442 U.S. 917, 99 S.Ct. 2836, 61 L.Ed.2d 283 (1979).
. In Trotter, this court refused to accept the Government’s suggestion that a less rigorous standard requiring only “prima facie proof" was appropriate in light of United States v. Nixon, 418 U.S. 683, 94 S.Ct. 3090, 41 L.Ed.2d 1039 (1974). •
. Once Gibbs was held to have participated in the conspiracy the telephone conversations referred to in text were properly admissible against Gibbs under Fed.R.Evid. 801(d)(2)(E). See Ammar, 714 F.2d at 245.
. White testified on direct examination that he "volunteered to go down and pick up 'Jake' with my — with an airplane, and Joe accepted the— the offer, ... and the next day I went down to the airport and met — met ‘Jake’.” App: 61a. This testimony would be admissible against Gibbs to link him to the conspiracy without running afoul of the hearsay rules.
. The defendant argued before this court, based on the record, that Gibbs was taken to Wings Airfield because it was convenient to Quintiliano’s residence. Accepting that as true does not alter the fact that a reasonable inference such as the Government suggests could be drawn from the circumstances described. At this point in time, the Government is entitled to the benefit of any reasonable inferences that may be drawn from the record. Glasser v. United States, 315 U.S. 60, 80, 62 S.Ct. 457, 469, 86 L.Ed. 680 (1941).
. It is true that mere association with those who have conspired cannot by itself support a conviction for conspiracy. See Ammar, 714 F.2d at 250; United States v. Torres, 519 F.2d 723, 726 (2d Cir.), cert. denied, 423 U.S. 1019, 96 S.Ct. 457, 46 L.Ed.2d 392 (1975). In the instant case, however, inferences are capable of being drawn which suggest that Gibbs' meeting with Quintiliano was "intended to advance the ends of the conspiracy.” See United States v. Mancillas, 580 F.2d 1301, 1308 (7th Cir.), cert. denied, 439 U.S. 958, 99 S.Ct. 361, 58 L.Ed.2d 351 (1978). In addition, it must be remembered that the Government's burden here was only to establish the existence of a conspiracy by a preponderance of the evidence.
. Direct evidence of Gibbs' relationship to Quintiliano in October 1980 consists of telephone records showing calls from the Quintiliano residence to the Gibbs residence or to Ram • Broadcast Co. at around that time. The Government suggests that from this series of telephone calls it can be inferred that Gibbs and Quintiliano were discussing arrangements for the sale *845of the marijuana in furtherance of whatever plans they had made at their April meeting. Gibbs argues otherwise. He claims that one obvious difficulty is the absence of evidence directly linking Gibbs with Ram or showing that any of Quintiliano’s calls were returned. Moreover, Gibbs asserts that except for Quintiliano’s hearsay, there is nothing to indicate the substance of the conversations, and the bare bone telephone toll records have little probative value.
. Defendants can also show "that the conspiracy terminated, such as by demonstrating that its ends had been so frustrated or its means so impaired that its continuation was no longer plausible.” Ammar, 714 F.2d at 254. There is no doubt in this case but that the drug smuggling conspiracy itself had not been terminated and was ongoing in October 1980.
. Gibbs claims the presumption of continuing involvement under Gillen is unconstitutional, citing United States v. Read, 658 F.2d 1225 (7th Cir.1981). Read, however, concerns the prosecution’s burden to prove every element of the offense beyond a reasonable doubt as a basis for a conviction and thus is not relevant to the lesser showing that must be made to permit the introduction of co-conspirator statements. Moreover, Read did impose on the defendant the burden of presenting some evidence of withdrawal. Id. at 1239. Here none was presented.
. Although Gibbs challenged the admissibility of Quintiliano's out-of-court statements and at the conclusion of the trial moved “to strike all of the hearsay coconspirator’s declarations,” on appeal Gibbs argues in support of his claim (that he had withdrawn from the conspiracy) that an alleged statement by Quintiliano to Bilella early in October 1980 — to the effect that Quintiliano had another potential buyer from Florida for the marijuana — is evidence that Gibbs had withdrawn from the conspiracy as early as April. This testimony, however, is a portion of the very evidence to which Gibbs objects.
. The only argument made by Gibbs challenging the reliability of the evidence is that Quintiliano had reason to, and did, fabricate Gibbs' involvement in the conspiracy. In Ohio v. Roberts, 448 U.S. 56, 100 S.Ct. 2531, 65 L.Ed.2d 597 (1980), the Supreme Court held that "the Confrontation Clause restricts the range of admissible hearsay by imposing a two-prong requirement: first, the government must normally show that the declarant is unavailable and that the hearsay testimony is thus necessary; and second, the statement must bear sufficient ‘indicia of reliability’ to demonstrate its trustworthiness." United States v. Ammar, 714 F.2d 238, 255 (3d Cir.), cert. denied, — U.S. -, 104 S.Ct. 344, 78 L.Ed.2d 311 (1983), citing Roberts, 448 U.S. at 65-66, 100 S.Ct. at 2538-39. Some members of the majority believe that the reliability component of the Roberts test should be addressed in this opinion, while others do not. See United States v. Ammar, 714 F.2d 238, 254-57 (3d Cir.1983) (decided after Gibbs’ trial). Regardless of that philosophical disagreement, all the members of the majority are in agreement that the Roberts reliability requirement, if preserved for appeal, was satisfied in this case. See Ammar, 714 F.2d at 256 ("[I]n many, if not most, instances a coconspirator statement which is admissible under Rule 801(d)(2)(E) will also be sufficiently reliable to satisfy the Confrontation Clause.’’). In short, we are not persuaded by Gibbs’ reliability argument.
. Rule 801(d)(2)(E) states only that "[a] statement is not hearsay if ... [tjhe statement is offered against a party and is ... a statement by a coconspirator of a party during the course and in furtherance of the conspiracy.”
. Rule 804(b) lists five hearsay exceptions which "are not excluded by the hearsay rule if the declarant is unavailable as a witness,” using the definition of "unavailable” found in Rule 804(a) (listing five categories of when a witness is to be deemed unavailable).
. In Belmont Industries, Inc. v. Bethlehem Steel Corp., 512 F.2d 434 (3d Cir.1975), testimony had been received without objection "at widely scattered times over [a] ten-day trial.” Id. at 437. Belmont moved after the close of Bethlehem’s case to strike considerable portions of testimony on hearsay and best-evidence grounds. In addition, like Gibbs, Belmont’s motion did not specify which of the items of testimony were to be stricken. Id. This court held:
We cannot say that the trial judge abused his discretion in determining that the possibilities of confusion to the jury, prejudice to the opposing party, and undue delay of a case about to be submitted to the jury outweighed the detriment suffered by Belmont resulting from the reception of this allegedly hearsay and secondary evidence.
Id. (footnote omitted).
The circumstances in Belmont Industries apply with equal force here. Certainly the prospects of confusion to the jury, prejudice to the Government, and undue delay are very real in this case, particularly since here Gibbs at no time made known the specific constitutional ground on which he now relies.
. Although we may entertain on appeal objections not timely raised below if the district court committed plain error, see Fed.R.Crim.Proc, 52(b); Halderman, supra, 673 F.2d at 639-40, we are satisfied that in this instance the district court did not commit plain error.