delivered the opinion of the Court.
This is a motion for leave to file in this Court the petition of the Republic of Peru for a writ of prohibition or of mandamus. The petition aslcs this Court to prohibit respondent, a judge of the District Court for the Eastern District of Louisiana, and the other judges and officers of that court, from further exercise of jurisdiction over a proceeding in rem, pending in that court against petitioner’s steamship Ucayali, and to direct the district judge to enter an order in the proceeding declaring the vessel immune from suit. The questions for decision here are whether this Court has jurisdiction to issue the writ, whether such jurisdiction should in our discretion be exercised in petitioner’s behalf, and whether petitioner’s appearance and defense of the suit in the district court was, as that court has ruled, a waiver of its claim that the vessel, being that of a friendly sovereign state, is im*580mune from suit brought by a private party in the court of the United States.
On March 30, 1942, Galban Lobo Co., S. A., a Cuban corporation, filed a libel in the district court against the Ucayali for its failure to carry a cargo of sugar from a Peruvian port to New York, as required by the terms of a charter party entered into by libelant with a Peruvian corporation acting as agent in behalf of the Peruvian Government. On April 9, 1942, the Republic of Peru, acting by the master of the vessel, intervened in the district court by filing a claim to the vessel, averring that the Republic of Peru was sole owner, and stating: “The filing of this claim is not a general appearance and is without prejudice to or waiver of all defenses and objections which may be available to respondent and claimant, particularly, but not exclusively, sovereign immunity.”
On the same day, petitioner procured the release of the vessel by filing a surety release bond in the sum of $60,000, on which petitioner was principal. The bond, which contained a reservation identical with that appearing in petitioner’s claim to the vessel, was conditioned upon payment of any amount awarded to libelant by the final decree in the cause. On April . 11th petitioner proceeded in the cause to take the testimony of the master on the merits, and spread on the record a statement that the testimony was taken with like “full reservation and without waiver of all defenses and objections which may be available to respondent and claimant, particularly, but not exclusively, sovereign immunity.” Petitioner also stated that “the appearance of counsel for the Government of Peru and the Steamship Ucayali is for the special purpose only of taking the testimony of the master under the reservation aforesaid.”
On April 18th, and again on May 10th and on May 29th, petitioner moved for and obtained an order of the district court extending its time within which to answer *581or otherwise plead to the libel. Each motion was made “with full reservation and without waiver of any defenses and objections which may be available to mover, particularly, but not exclusively, sovereign immunity.”
In the meantime, petitioner, following the accepted course of procedure (see Ex parte Muir, 254 U. S. 522; Compania Espanola v. The Navemar, 303 U. S. 68), by appropriate representations, sought recognition by the State Department of petitioner’s claim of immunity, and asked that the Department advise the Attorney General of the claim of immunity and that the Attorney General instruct the United States Attorney for the Eastern District of Louisiana to file in the district court the appropriate suggestion of immunity of the vessel from suit. These negotiations resulted in formal recognition by the State Department of the claim of immunity. This was communicated to the Attorney General by the Under Secretary’s letter of May 5, 1942. The letter requested him to instruct the United States Attorney to present to the district court a copy of the Ambassador’s formal claim of immunity filed with the State Department, and to say that “this Department accepts as true the statements of the Ambassador concerning the steamship Ucayali, and recognizes and allows the claim of immunity.”
Pursuant to these instructions the United States Attorney, on June 29th, filed in the district court a formal statement advising the court of the proceedings and communications mentioned, suggesting to the court and praying “that the claim of immunity made on behalf of the said Peruvian Steamship Ucayali and recognized and allowed by the State Department be given full force and effect by this court”; and “that the said vessel proceeded against herein be declared immune from the jurisdiction and process of this court.” On July 1st, petitioner moved for release of the vessel and that the suit be dismissed. The district court denied the motion on the ground that peti*582tioner had waived its immunity by applying for extensions of time within which to answer, and by taking the deposition of the master — steps which the district court thought constituted a general appearance despite petitioner’s attempted reservation of its right to assert its immunity as a defense in the suit. 47 F. Supp. 203.
The first question for our consideration is that of our jurisdiction. Section 13 of the Judiciary Act of 1789, 1 Stat. 81, conferred upon this Court “power to issue writs of prohibition to the district courts, when proceeding as courts of admiralty and maritime jurisdiction, and writs of mandamus, in cases warranted by the principles and usages of law, to any courts appointed, or persons holding office, under the authority of the United States.” And § 14 provided that this Court and other federal courts “shall have power to issue writs of scire facias, habeas corpus, and all other writs not specially provided for by statute, which may be necessary for the exercise of their respective jurisdictions, and agreeable to the principles and usages of law.” 1 Stat. 81. These provisions have in substance been carried over into §§ 234 and 262 of the Judicial Code (28 U. S. C. §§ 342, 377), and § 751 of the Revised Statutes (28 U. S. C. § 451).
The jurisdiction of this Court as defined in Article III, § 2, of the Constitution is either “original” or “appellate.” Suits brought in the district courts of the United States, not of such character as to be within the original jurisdiction of this Court under the Constitution, are cognizable by it only in the exercise of its appellate jurisdiction. Hence, its statutory authority to issue writs of prohibition or mandamus to district courts can be constitutionally exercised only insofar as such writs are in aid of its appellate jurisdiction. Marbury v. Madison, 1 Cranch 137, 173-80; Ex parte Siebold, 100 U. S. 371, 374-75.
Under the statutory provisions, the jurisdiction of this Court to issue common-law writs in aid of its appellate *583jurisdiction has been consistently sustained. The historic use of writs of prohibition and mandamus directed by an appellate to an inferior court has been to exert the revisory appellate power over the inferior court. The writs thus afford an expeditious and effective means of confining the inferior court to a lawful exercise of its prescribed jurisdiction, or of compelling it to exercise its authority when it is its duty to do so. Such has been the office of the writs when directed by this Court to district courts, both before the Judiciary Act of 1925, 43 Stat. 936,1 and since.2 In all these-cases (cited in notes 1 and 2), the appellate, not the original, jurisdiction of this Court was invoked and exercised.3
*584The common law writs, like equitable remedies, may be granted or withheld in the sound discretion of the Court, Ex parte Skinner & Eddy Corp., 265 U. S. 86, 95-96; Ex parte City of Monterey, 269 U. S. 527; Maryland v. Soper (No. 1), 270 U. S. 9, 29; United States v. Dern, 289 U. S. 352, 359, and are usually denied where other adequate remedy is available. Ex parte Baldwin, 291 U. S. 610. And ever since the statute vested in the circuit courts of appeals appellate jurisdiction on direct appeal from the district courts, this Court, in the exercise of its discretion, has in appropriate circumstances declined to issue the writ to a district court, but without prejudice to an application to the circuit court of appeals (Ex parte Apex Mfg. Co., 274 U. S. 725; Ex parte Daugherty, 282 U. S. 809; Ex parte Krentler-Arnold Hinge Last Co., 286 U. S. 533), which likewise has power under § 262 of the Judicial Code to issue the writ. McClellan v. Carland, 217 U. S. 268; Adams v. U. S. ex rel. McCann, 317 U. S. 269.
After a full review of the traditional use of the common-law writs by this Court, and in issuing a writ of mandamus, in aid of its appellate jurisdiction, to compel a district judge to issue a bench warrant in conformity to statutory requirements, this Court declared in Ex parte United States, 287 U. S. 241, 248-49: “The rule deducible from the later decisions, and which we now affirm, is, that this Court has full power in its discretion to issue the writ of mandamus to a federal district court, although the case be one in respect of which direct appellate jurisdiction is *585vested in the circuit court of appeals — this Court having ultimate discretionary jurisdiction by certiorari — but that such power will be exercised only where a question of public importance is involved, or where the question is of such a nature that it is peculiarly appropriate that such action by this Court should be taken. In other words, application for the writ ordinarily must be made to the intermediate appellate court, and made to this Court as the court of ultimate review only in such exceptional cases.” 4
*586We conclude that we have jurisdiction to issue the writ as prayed. And we think that — unless the sovereign immunity has been waived — the case is one of such public importance and exceptional character as to call for the exercise of our discretion to issue the writ rather than to relegate the Republic of Peru to the circuit court of appeals, from which it might be necessary to bring the case to this Court again by certiorari. The case involves the *587dignity and rights of a friendly sovereign state, claims against which are normally presented and settled in the course of the conduct of foreign affairs by the President and by the Department of State. When the Secretary elects, as he may and as he appears to have done in this case, to settle claims against the vessel by diplomatic negotiations between the two countries rather than by continued litigation in the courts, it is of public importance that the action of the political arm of the Government taken within its appropriate sphere be promptly recognized, and that the delay and inconvenience of a prolonged litigation be avoided by prompt termination of the proceedings in the district court. If the Republic of Peru has not waived its immunity, we think that there are persuasive grounds for exercising our jurisdiction to issue the writ in this case and at this time without requiring petitioner to apply to the circuit court of appeals, and that those grounds are at least as strong and urgent as those found sufficient in Ex parte United States, in Maryland v. Soper, in Colorado v. Symes, and in McCullough v. Cosgrave, all supra, note 2. We accordingly pass to the question whether petitioner has waived his immunity.
This case presents no question of the jurisdiction of the district court over the person of a defendant. Such jurisdiction must be acquired either by the service of process or by the defendant’s appearance or participation in the litigation. Here the district court acquired jurisdiction in rem by the seizure and control of the vessel, and the libelant’s claim against the vessel constituted a case or controversy which the court had authority to decide. Indeed, for the purpose of determining whether petitioner was entitled to the claimed immunity, the district court, in the absence of recognition of the immunity by the Department of State, had authority to decide for itself whether all the requisites for such immunity existed— *588whether the vessel when seized was petitioner’s, and was of a character entitling it to the immunity. See Ex parte Muir, supra; The Pesaro, 255 U. S. 216; Berizzi Bros. Co. v. The Pesaro, 271 U. S. 562; Compania Espanola v. The Navemar, supra. Therefore the question which we must decide is not whether there was jurisdiction in the district court, acquired by the appearance of petitioner, but whether the jurisdiction which the court had already acquired by seizure of the vessel should have been relinquished in conformity to an overriding principle of substantive law.
That principle is that courts may not so exercise their jurisdiction, by the seizure and detention of the property of a friendly sovereign, as to embarrass the executive arm of the Government in conducting foreign relations. “In such cases the judicial department of this government follows the action of the political branch, and will not embarrass the latter by assuming an antagonistic jurisdiction.” United States v. Lee, 106 U. S. 196, 209. More specifically, the judicial seizure of the vessel of a friendly foreign state is so serious a challenge to its dignity, and may so affect our friendly relations with it, that courts are required to accept and follow the executive determination that the vessel is immune. When such a seizure occurs the friendly foreign sovereign may present its claim of immunity by appearance in the suit and by way of defense to the libel. Compania Espanola v. The Navemar, supra, 74 and cases cited; Ex parte Muir, supra. But it may also present its claim to the Department of State, the political arm of the Government charged with the conduct of our foreign affairs. Upon recognition and allowance of the claim by the State Department and certification of its action presented to the court by the Attorney General, it is the court’s duty to surrender the vessel and remit the libelant to the relief obtainable through diplomatic negotiations. Compania Espanola v. The Navemar, supra, *58974; The Exchange, 7 Cranch 116. This practice is founded upon the policy, recognized both by the Department of State and the courts, that our national interest will be better served in such cases if the wrongs to suitors, involving our relations with a friendly foreign power, are righted through diplomatic negotiations rather than by the compulsions of judicial proceedings.
We cannot say that the Republic of Peru has waived its immunity. It has consistently declared its reliance on the immunity, both before the Department and in the district court. Neither method of asserting the immunity is incompatible with the other. Nor, in view of the purpose to be achieved by permitting the immunity to be asserted, are we able to perceive any ground for saying that the district court should disregard the claim of immunity, which a friendly sovereign is authorized to advance by way of defense in the pending suit, merely because the sovereign has seen fit to preserve its right to interpose other defenses. The evil consequences which might follow the seizure of the vessel are not any the less because the friendly state asserts other grounds for the vessel’s release.
Here the State Department has not left the Republic of Peru to intervene in the litigation through its Ambassador as in the case of Compania Espanola v. The Navemar. The Department has allowed the claim of immunity and caused its action to be certified to the district court through the appropriate channels. The certification and the request that the vessel be declared immune must be accepted by the courts as a conclusive determination by the political arm of the Government that the continued retention of the vessel interferes with the proper conduct of our foreign relations. Upon the submission of this certification to the district court, it became the court’s duty, in conformity to established principles, to release the vessel and to proceed no further in the cause. We *590have no occasion to decide whether the court should surrender the vessel and dismiss the suit on certification of sovereign immunity by the Secretary, made after the friendly sovereign has once unqualifiedly assented to a judicial determination of the controversy.
The motion for leave to file is granted. We assume that, in view of this opinion, formal issuance of the writ will be unnecessary, and we direct that the writ issue only on further application by the petitioner.
Mr. Justice Roberts concurs in the result.E. g., Ex parte State of New York, No. 1, 256 U. S. 490; The Western Maid, 257 U. S. 419; Ex parte Simons, 247 U. S. 231; Ex parte Peterson, 253 U. S. 300, 305; Ex parte Hudgings, 249 U. S. 378; Ex parte Uppercu, 239 U. S. 435; Matter of Heff, 197 U. S. 488; Ex parte Siebold, 100 U. S. 371; Ex parte Watkins, 3 Pet. 193; United States v. Peters, 3 Dall. 121.
Ex parte United States, 287 U. S. 241; Maryland v. Soper (No. 1), 270 U. S. 9, 27-28; Maryland v. Soper (No. 2), 270 U. S. 36; Maryland v. Soper (No. 3), 270 U. S. 44; Colorado v. Symes, 286 U. S. 510; McCullough v. Cosgrave, 309 U. S. 634; Ex parte Kawato, 317 U. S. 69; see Los Angeles Brush Corp. v. James, 272 U. S. 701.
See particularly the discussion in Maryland v. Soper (No. 1), 270 U. S. 9, 28-30, and in Ex parte United States, 287 U. S. 241. Compare Ex parte Siebold, 100 U. S. 371.
Ex parte United States, supra, was not and could not have been a case of original jurisdiction. The Constitution confers original jurisdiction only in cases affecting ambassadors, other public ministers and consuls, and “those in which a State shall be Party” (Art. Ill, § 2, cl. 2). No state was made a party to Ex parte United States. The United States has never been held to be a “State” within this provision — and it obviously is not — nor has it any standing to bring an original action in this Court which does not otherwise come within one of the provisions of Article III, § 2, cl. 2. United States v. Texas, 143 U. S. 621, relied upon to sustain a different view, was within the original jurisdiction because the State of Texas was the party defendant. And *584until now it has never been suggested that necessity, however great, warrants the exercise by this Court of original jurisdiction which the Constitution has not conferred upon it. Moreover, even if Congress had withdrawn this Court’s appellate jurisdiction by the 1925 Act, there would have been no necessity in Ex parte United States for inventing an original jurisdiction which the Constitution had withheld, since a writ of mandamus could have been applied for in the circuit court of appeals.
The suggestion that the Judiciary Act of 1925 was intended to curtail the jurisdiction previously exercised by this Court in granting such writs to the district courts finds no support in the history or language of the Act. The Act was originally prepared by a committee of justices of this Court, by whom it was submitted to Congress for consideration. Four members of this Court gave testimony before Congressional committees in explanation of the purposes and meaning of the Act, and Chief Justice Taft submitted a detailed statement of the changes which the Act would effect. These disclose that the great purpose of the Act was to curtail the Court’s obligatory jurisdiction by substituting, for the appeal as of right, discretionary review by certiorari in many classes of cases. In all the oral and written submissions by members of this Court, and in the reports of the committees of Congress which recommended adoption of the bill, there is not a single suggestion that the Act would withdraw or limit the Court’s existing jurisdiction to direct the common-law writs to the district courts when, in the exercise of its discretion, it deemed such a remedy appropriate. See Résumé, together with Citations Affecting Sections of Senate Bill 3164, submitted by Chief Justice Taft, printed for use of Senate Committee on the Judiciary, 67th Cong., 2d Sess.; Hearing on S. 2060 and S. 2061, before a Subcommittee of the Senate Committee on the Judiciary, Feb. 2, 1924, 68th Cong., 1st Sess.; Hearing on H. R. 8206 before House Committee on the Judiciary, Dec. 18, 1924, 68th Cong., 2d Sess.; S. Rep. No. 362, 68th Cong., 1st Sess.; H. Rep. No. 1075, 68th Cong., 2d Sess. The changes in existing law proposed to be made by the Act were set forth with painstaking detail. It is hardly conceivable that the justices of this Court, fully familiar with its practice, would have left unexpressed an intention — had such intention really existed — to curtail drastically a jurisdiction which the Court had exercised under statutory
*586authority from the beginning of its history. Ex parte United States, and most of the other cases cited in note 2, supra, were decided at a time when members of the Court’s committee responsible for the 1925 Act were still members of the Court. The Court’s unanimous concurrence in the existence of its jurisdiction in the cases subsequent to the 1925 Act establishes a practice (cf. Stuart v. Laird, 1 Cranch 299, 309) which would be beyond explanation if there had been any thought that any provision of the Act had placed such a restriction on the Court’s jurisdiction to issue the writs.
Nor can it be said that this legislative history gives any support to the suggestion that the failure of the 1925 Act to cut off the jurisdiction of this Court to issue the common-law writs to district courts was inadverent, and that the Act should therefore be construed as though it had done what it failed to do. The jurisdiction of this Court to issue such writs, like its jurisdiction to grant certiorari, is discretionary. The definite aim of the 1925 Act was to enlarge, not to destroy, the Court’s discretionary jurisdiction. That aim can hardly give rise to an inference of an unexpressed purpose to amend or repeal the statutes of the United States conferring jurisdiction on the Court to issue the writs, or an inference that such would have been the purpose had repeal been proposed. The exercise of that jurisdiction has placed no undue burden on this Court. It is significant that, since 1925, less than ten of the numerous applications to this Court for such writs have been granted. Only in rare instances has their denial been the occasion for an opinion dealing with questions of public importance. See, e. g., Los Angeles Brush Corp. v. James, 272 U. S. 701; Ex parte Baldwin, 291 U. S. 610; Ex parte Colonna, 314 U. S. 510; cf. Mooney v. Holohan, 294 U. S. 103. And whatever the scope of the jurisdiction of this Court, in no case does it decline to examine an application in order to determine whether it has jurisdiction.