It was the first clear-cut evidence that Mr. Comey believed the bureau needed more resources to handle a sprawling and highly politicized counterintelligence investigation.
His appeal, described on Wednesday by four congressional officials, was made to Rod J. Rosenstein, the deputy attorney general, whose memo was used to justify Mr. Comey's abrupt dismissal on Tuesday.
It is not yet known what became of Mr. Comey's request, or what role _ if any _ it played in his firing. But the future of the F.B.I.'s investigation is now more uncertain than at any point since it began in late July, and any fallout from the dismissal is unlikely to be contained at the bureau.