The deal would also restrict gold-plated farewells for executives of companies that sell devalued assets to the Treasury Department.

Image Senator Judd Gregg, Republican of New Hampshire, said of the new plan, If we dont pass it, we shouldnt be a Congress. Credit... Andrew Councill for The New York Times

President Bush called the measure “a very good bill” and praised Congressional leaders. “This plan sends a strong signal to markets around the world that the United States is serious about restoring confidence and stability to our financial system,” Mr. Bush said in a statement. “Without this rescue plan, the costs to the American economy could be disastrous.”

House Republicans had threatened to scuttle the deal, and proposed a vastly different approach that would have focused on insuring troubled debt rather than buying it. In the end, the insurance proposal was included on top of the purchasing power, but there is no requirement that the Treasury secretary use it, leaving them short of that goal.

It is virtually impossible to know the ultimate cost of the rescue plan to taxpayers, but Congressional leaders stressed that it would likely be far less than $700 billion. Because the Treasury will buy assets with the potential to resell them at a higher price, the government might even turn a profit.

That provision, pushed by House Democrats, was the last to be agreed to in a high-level series of talks that had top lawmakers and White House economic advisers hustling between offices just off the Capitol Rotunda until midnight on Saturday, scrambling to strike an agreement before Asian markets opened Sunday night.

The bill calls for disbursing the money in parts, starting with $250 billion followed by $100 billion at the discretion of the president. The Treasury can request the remaining $350 billion at any time, and Congress must act to deny it if it disapproves.

The agreement on a bailout plan was greeted with subdued optimism in early Asian trading on Monday. But shares sank by late Monday morning on renewed worries about the credit crisis, with a decision by HSBC to raise lending rates by 0.5 percent in Hong Kong triggering a drop of 2 percent in the Hang Seng Index in Hong Kong and 0.9 percent in the Kospi Index in Seoul.