General Motors Corp., the world's largest automaker until its 77-year reign ended in 2008, plans to file for bankruptcy protection Monday and sell most of its assets to a new, reorganized GM, people familiar with the matter said yesterday.

GM's path will be smoothed by an accord yesterday giving some of its biggest bondholders an equity stake in the reorganized automaker. The U.S. Treasury is requiring that an unspecified percentage of debt holders accept the terms by 5 p.m. tomorrow, GM said in a regulatory filing.

"If bondholders agree to this up front, this would essentially be a prepackaged bankruptcy," said Shelly Lombard, an analyst with New York-based bond-research firm Gimme Credit L.L.C. "GM could exit Chapter 11 faster." In a prepackaged bankruptcy, the parties agree to the terms of a company's reorganization in advance.

In a related development, GM is to announce Monday morning which of its 14 more plants it will close as it slashes production and costs, one of the people briefed on the plans said yesterday. The sources asked not to be identified because the plans have not been made public.

GM has said it plans to close 16 U.S. factories by the end of next year, shedding 21,000 jobs. Two have already been announced - an engine plant in Massena, N.Y., and a parts stamping plant near Grand Rapids, Mich.

Battered by almost $88 billion in losses since 2004, GM fell short in a bid to cut its debt $44 billion under a government deadline to restructure outside court by Monday. The 100-year-old automaker seeks to rebuild around assets such as its Cadillac and Chevrolet brands as it follows Chrysler L.L.C. into bankruptcy. The company lost its spot as the largest automaker to Toyota Motor Corp.

Company vice chairman Bob Lutz, while not confirming GM's intentions or a possible bankruptcy venue, said any court restructuring would be quick.

"We intend to get in and out very soon," he said yesterday at an Automotive Press Association luncheon in Detroit. "The U.S. government wants its money back, and our plan is to pay it back as quickly as possible. The U.S. government doesn't want to own auto companies."

The Treasury will finance the trip through bankruptcy with about $50 billion, which includes $19.4 billion in current borrowing, GM said in a statement.

The administration's goal is for GM to eventually return to profitability, allowing the government to sell its stake in the company. But the risks for taxpayers are daunting, with U.S. auto sales near their lowest in 27 years.

Going to Bankruptcy Court would end the suspense for GM, which has said it expects to declare bankruptcy after failing to get enough support for its original debt-for-equity exchange on $27.2 billion in unsecured bonds.

Only 15 percent of bondholders approved the original offer to trade their debt for a 10 percent stake in the new GM, a person familiar with the matter said. GM sweetened the plan yesterday to promise warrants good for buying 15 percent more of the new enterprise, which would have an improved balance sheet based on a U.S. plan to trade bailout loans for equity.