US President Bush and the two men fighting to succeed him joined forces Thursday at a historic White House meeting on a multibillion-dollar Wall Street bailout plan, aiming to stave off a national economic disaster. Key members of the US Congress said they had struck a deal earlier in the day, but its future was unclear.

US President George W. Bush (L) makes remarks during a meeting with members of congress including the Presidential candidates Republican John McCain and Barack Obama (R) in the Cabinet Room at the White House in Washington, DC. [Agencies]

The tentative accord would give the Bush administration just a fraction of the $700 billion it had requested up front, with half that total subject to a congressional veto, Capitol Hill aides said. But nothing appeared final. Amid several signs that conservatives were balking, Sen. Richard Shelby of Alabama, the top Republican on the Senate Banking Committee, emerged from the White House and said the announced agreement "is, obviously, no agreement."

Both of Congress' Republican leaders, Rep. John Boehner and Sen. Mitch McConnell, issued statements saying there was not yet an agreement.

Democrat Barack Obama and Republican John McCain, who have both sought to distance themselves from the unpopular Bush, sat down with the president at the White House for an hourlong afternoon session that was striking in this brutally partisan season and apparently without precedent. By also including Congress' Democratic and Republican leaders, the meeting gathered nearly all Washington's political power structure at one long table in a small West Wing room.

"All of us around the table ... know we've got to get something done as quickly as possible," Bush told reporters, brought in for only the start of the meeting. Obama and McCain were at distant ends of the oval table, not even in each other's sight lines. Bush, playing host in the middle, was flanked by Congress' two Democratic leaders, House Speaker Nancy Pelosi and Senate Majority Leader Harry Reid.

No one else spoke, and all the visitors left the White House without talking to a huge media group gathered outside.

Hours earlier, private talks on Capitol Hill ended with the announcement that an agreement in principle had been reached on a financial rescue package – though changed from what the Bush administration proposed last weekend by near-daily concessions to demands from the right and the left.