Order and judgment (one paper), Supreme Court, New York County (Harold Tompkins, J.), entered on or about October 17, 1991, which denied petitioner’s application for a stay of arbitration and dismissed the petition, unanimously affirmed, with costs.
Petitioner withdrew its claim that the offending vehicle was uninsured after it was shown that the basis of the demand for arbitration was underinsurance. Because the initial petition *278did not assert a claim of underinsurance, the IAS Court properly denied the application for a stay as untimely. Application of the doctrine of relation back, sua sponte, would have been inappropriate. In any event, petitioner failed to make out a prima facie case for a stay of arbitration (see, Matter of Prudential Prop. & Cas. Ins. Co. v Mortise, 178 AD2d 646). Concur — Milonas, J. P., Rosenberger, Ross and Asch, JJ.