The details of those plans continued to be worked out on Saturday, when the Federal Reserve chairman, Ben S. Bernanke, met with Paulson, Lockhart and key company executives in Washington.

While Freddie Mac's accounting woes make it easier for regulators to force the company into conservatorship, there was more resistance from Fannie Mae, according to people familiar with the discussions. Once the government took action against Freddie Mac, however, confidence in Fannie Mae would certainly waver. Given Fannie Mae's declining financial condition, the company has few options but to concede to the government's demands.

Both companies have the option of challenging the conservatorship and asking for a judicial review.

Accusations of questionable accounting are not new for either company. Earlier this decade, both companies paid large fines and ousted their top executives after accounting scandals.

Freddie Mac's current chief executive and chairman, Richard F. Syron, joined the company in 2003 after the former managers revealed they had manipulated earnings by almost $5 billion.

The following year Fannie Mae's chief executive, Daniel H. Mudd, was promoted to the top spot after that company was accused of accounting errors totaling $6.3 billion. People familiar with Treasury's plan say that both men, as well as other executives, will be forced to leave the companies.

The accounting issues that brought so much urgency to the bailout appear to center on Freddie Mac's capital cushion, the assets that regulators require them to keep on hand to cover losses.

The methods used to bolster that cushion have caused serious concerns among the companies' regulators, outside auditors and some investors. For example, while Freddie Mac's portfolio contains many securities backed by subprime loans, made to the riskiest borrowers, and alt-A loans, one step up on the risk ladder, the company has not written down the value of many of those loans to reflect current market prices.

Executives have said that they intended to hold the loans to maturity, meaning they would be worth more, and they needed not write down their value. But other financial institutions have written down similar securities, to comply with "mark-to-market" accounting rules. Freddie Mac holds roughly twice as many of those securities as Fannie Mae.

Freddie Mac and Fannie Mae have also inflated their financial positions by relying on deferred-tax assets — credits accumulated over the years that can be used to offset future profits. Fannie maintains that its worth is increased by $36 billion through such credits, and Freddie argues that it has a $28 billion benefit.