WASHINGTON -- Congressional leaders and the Bush administration have reached a tentative deal on a bailout of imperiled financial markets that could cost taxpayers hundreds of billions of dollars.

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The House could vote on it Sunday and the Senate on Monday.

House Speaker Nancy Pelosi announced the accord just after midnight Saturday and said it still has to be put on paper.

Treasury Secretary Henry Paulson talked of finalizing the deal but added: "I think we're there."

The plan would spend up to $700 billion, most of it on buying deeply devalued mortgages from the housing market's collapse and other bad loans held by tottering banks and other investors.

The goal is to strike a deal before stock markets around the world begin a new week.

A key sticking point has been a new government-sponsored insurance program for lenders, demanded by House Republicans as an alternative to devoting the entire $700 billion to buying up toxic debt.

For one thing, Democrats and administration officials said they're willing to include the Republicans' idea of having the government insure distressed mortgage-backed securities. But that would only be an option, not a replacement for the broader idea of buying up those securities.

"While we do believe that the Congress needs to act to avert this crisis, we also believe that we should not be bailing out Wall Street on the backs of American taxpayers," said U.S. Rep John Boehner, R-Ohio.

The House is scheduled to convene at 1 p.m. Eastern Sunday.

Members are hoping to vote on the bailout by Sunday evening and go home to campaign for re-election. The Senate isn't scheduled to be back in session until Monday morning.

Earlier Saturday, Pelosi said she hoped to finish work Saturday so citizens could read the bill on Sunday.

"It would be my hope that this could be resolved today. That we have a day for the American people and members of Congress to review the legislation on the Internet and that we could bring something to the floor, possibly Sunday night or Monday morning. That is my hope, I hope that the progress being made here today would take us to that point," Pelosi said.

Bush Says He'd Love To Let Firms Collapse, But Can't

Would you rather just let irresponsible financial firms get what's coming to them instead of bailing them out?

President George W. Bush said he knows how you feel. In his radio address, he said if he could just let the irresponsible firms collapse, without affecting American families, he'd do it. But he said that's not possible.

"The failure of the financial system would cause banks to stop lending money to one another and to businesses and consumers," Bush said, according to a transcript of his address. "That would make it harder for you to take out a loan or borrow money to expand a business. The result would be less economic growth and more American jobs lost. And that would put our economy on the path toward a deep and painful recession."

Bush acknowledged that many Americans are frustrated by the situation that led to a possible bailout. And he knows people are angry that they may have to cover the mistakes of Wall Street firms.

"The rescue effort we're negotiating is not aimed at Wall Street -- it is aimed at your street," Bush said.

But he's calling on lawmakers from both sides to work together on what he calls "an issue that transcends partisanship." Bush said he's confident that there will be agreement on a plan to "protect the financial security of every American very soon."