DETROIT -- General Motors Corp. on Saturday readied for a bankruptcy filing amid signs that a majority of its largest creditors had backed a revised debt-equity exchange, a move that would potentially smooth its progress through court.

The company, the U.S. Treasury and an ad hoc committee representing large institutional creditors all declined comment after the expiration of a 5 p.m. EDT deadline for acceptance of the exchange. However, one member of the ad hoc committee said Saturday that the sweetened deal was expected...