On Sunday, Mr. Paulson defended the plan and the administration’s decision to expand it to protect foreign companies and authorize even wider latitude to buy assets other than those that were backed by mortgages.

Mr. Paulson, a former Wall Street deal maker, also suggested that the administration would have some flexibility in dealing with concerns raised by Congress.

Image Treasury Secretary Henry Paulson Jr. after appearing on This Week With George Stephanopoulos on Sunday. Credit... Lauren Victoria Burke/Associated Press

Democrats said the plan would need to provide more specific relief for troubled homeowners. They said the program, which the administration proposed to be run by Treasury, would have to be more accountable to Congress. And they said that the plan must restrict the compensation of corporate executives from companies that make use of the program to sell the burdensome securities on their balance sheets to the United States.

“We need to offer some assurance to the American taxpayer that Congress is watching,” Senator Christopher J. Dodd, Democrat of Connecticut and chairman of the banking committee, told reporters on Sunday. “One of the things that got us into this mess was the lack of accountability and the lack of oversight that was occurring, and I don’t think we want to repeat those mistakes with a program of this magnitude.”

Mr. Paulson said he hoped that the government would recoup much of the cost of buying distressed mortgage-related assets. But he did not rule out that the initial cost of the bailout could rise beyond $700 billion, the limit set in the terse proposal sent by the Treasury to Congress on Saturday.

“That doesn’t mean we’ll go all the way there, or it doesn’t mean it will stop there and we won’t ask for more,” Mr. Paulson said on the CBS program “Face the Nation.” “What we need is something that is big enough to get the job done. We’ll ask for what we think is a right amount to give us plenty of flexibility.”