WASHINGTON - Congressional leaders and the White House agreed Sunday to a $700 billion rescue of the ailing financial industry after lawmakers insisted on sharing spending controls with the Bush administration. The biggest U.S. bailout in history won the tentative support of both presidential candidates and goes to the House for a vote Monday.

The plan, bollixed up for days by election-year politics, would give the administration broad power to use billions upon billions of taxpayer dollars to purchase devalued mortgage-related assets held by cash-starved financial firms.

President Bush called the vote a difficult one for lawmakers but said he is confident Congress will pass it. "Without this rescue plan, the costs to the American economy could be disastrous," Bush said in a written statement released by the White House. He was to speak publicly about the plan early Monday morning, before U.S. markets open.

Flexing its political muscle, Congress insisted on a stronger hand in controlling the money than the White House had wanted. Lawmakers had to navigate between angry voters with little regard for Wall Street and administration officials who warned that inaction would cause the economy to seize up and spiral into recession.

A deal in hand, Capitol Hill leaders scrambled to sell it to colleagues in both parties and acknowledged they were not certain it would pass. "Now we have to get the votes," said Sen. Harry Reid, D-Nev., the majority leader.

Rep. John A. Boehner, R-Ohio, the House minority leader, said he was urging "every member whose conscience will allow them to support this" to back it, but officials in both parties expected the vote to be a nail-biter.

The final legislation was released Sunday evening, and Republicans and Democrats huddled for hours in private meetings to learn its details and voice their concerns.

Many said they left undecided, and leaders were scrambling to put the most positive face on a deeply unpopular plan.

"This isn't about a bailout of Wall Street, it's a buy-in, so that we can turn our economy around," said House Speaker Nancy Pelosi, D-Calif.

The largest government intervention in financial markets since the Great Depression casts Washington's long shadow over Wall Street. The government would take over huge amounts of devalued assets from beleaguered financial companies in hopes of unlocking frozen credit.

"I don't know of anyone here who wants the center of the economic universe to be Washington," said a top negotiator, Sen. Chris Dodd, chairman of the Senate Banking, Housing and Urban Affairs Committee. But, he added, "The center of gravity is here temporarily. ... God forbid it's here any longer than it takes to get credit moving again."

The plan would let Congress block half the money and force the president to jump through some hoops before using it all. The government could get at $250 billion immediately, $100 billion more if the president certified it was necessary, and the last $350 billion with a separate certification , and subject to a congressional resolution of disapproval.

Still, the resolution could be vetoed by the president, meaning it would take extra-large congressional majorities to stop it.

As Bush's team stepped up its efforts to corral reluctant Republicans, the White House released a letter from his budget chief, Jim Nussle, to Boehner saying the measure would cost taxpayers "considerably less" than its eye-popping $700 billion total.

Lawmakers in both parties were poring over the 110-page bill. Democratic leaders have made it clear they will not support the rescue unless a substantial number of Republicans join them.

"It will take two to make this work," said Rep. Rahm Emanuel, D-Ill.

But it was a tough sell for lawmakers in both parties.

Rep. Joe Barton, R-Texas, an opponent, estimated that half of the House's 199 Republicans are "truly undecided."

Lawmakers who struck a post-midnight deal on the plan with Treasury Secretary Henry Paulson predicted final congressional action might not come until Wednesday.

The proposal is designed to end a vicious downward spiral that has battered all levels of the economy. Hundreds of billions of dollars in investments based on mortgages have soured and cramped banks' willingness to lend.