WASHINGTON, April 26: Both chambers of the US Congress have passed legislation that would require the administration to start withdrawing troops from Iraq by Oct 11, setting the stage for a historic showdown with President George W. Bush.

The Senate voted 51-46 on Thursday to approve the $124.2 billion supplemental war spending bill, attaching the withdrawal clause despite warnings from President Bush that he would veto any move to set a timetable for pulling out troops from Iraq.

The House of Representatives approved this bill on Wednesday night on a 218-208 vote and sent it to the Senate to complete the mandatory legislative procedure. In both the chambers, the votes were largely along party lines and fell far short of the two-thirds margin needed to overturn the president’s threatened veto.

Also on Thursday, Senate Republicans promised to uphold President Bush’s veto while the Democrats said they would continue their efforts to end an unnecessary war.

“The president has failed in his mission to bring peace and stability to the people of Iraq,” said Senator Robert Byrd, a senior Democrat who chairs the Appropriations Committee.

The Republicans, however, blamed the Democrats for pushing American towards a defeat. The withdrawal dates in the bill "would be the day that Al Qaeda would declare victory ... and much the world would agree," said Republican Senator Sam Brownback.

The US military, however, has refused to be a party to this legislative wrangle, although the emergency spending funds disputed between the two parties will have a direct bearing on its ability to fight the war.

“I have tried to stay clear of the political minefields of various legislative proposals,” Gen David Petraeus, top US commander in Iraq, told a Pentagon news conference when asked about the impact of this legislation on the war.