WASHINGTON -- After rancorous debate, the U.S. House has approved legislation challenging President George W. Bush to pull U.S. troops out of Iraq by fall 2008.

Related: Video | Roll Call | Interactive | Timetable?

The vote was 218-212, mostly along party lines, to approve the Defense Department's emergency fiscal 2007 supplemental $93.4 billion request to help fund U.S. forces in Iraq, Afghanistan and elsewhere. The bill also requires that U.S. combat troops be out of Iraq by Aug. 31, 2008, and includes some domestic spending measures. (Click here to see the roll call of the vote.)

Democrats cast the vote as supporting the troops but requiring that they be brought home to encourage the Iraqis to take over their own security. It represented Congress' boldest challenge yet to the administration's war strategy.

"(Timelines) are the instrument by which we communicate to the Iraqi politicians that they must begin to resolve their differences. They must step up because we are not going to run our baby-sitting service forever," said Rep. David Obey, D-Wis., and chairman of the House Appropriations Committee.

At a hastily convened news conference, Bush dismissed the vote a matter of "political theater" and said the House of Representatives "abdicated its responsibility" to the troops by approving legislation that stands "no chance of becoming law."

"A narrow majority in the House of Representatives abdicated its responsibility by passing a war spending bill that has no chance of becoming law and brings us no closer to getting the troops the resources they need to do their job," Bush said.

"These Democrats believe that the longer they can delay funding for our troops, the more likely they are to force me to accept restrictions on our commanders, an artificial timetable for withdrawal and their pet spending projects. This is not going to happen," the president said.

But Democrats said it was time to heed the mandate of their election sweep last November, which gave them control of Congress.

"The American people have lost faith in the president's conduct of this war," House Speaker Nancy Pelosi, D-Calif., said after the vote was tallied. "The American people see the reality of the war; the president does not."

Their narrow victory indicated that they did not have the votes to overcome a presidential veto, which Bush again promised.

"As I have made clear for weeks, I will veto it if it comes to my desk. And because the vote in the House was so close, it is clear that my veto would be sustained. Today's action in the House does only one thing: It delays the delivering of vital resources for our troops. A narrow majority has decided to take this course, just as General Petraeus and his troops are carrying out a new strategy to help the Iraqis secure their capital city," Bush said.

A Senate committee approved a $122 billion measure Thursday financing wars in Iraq and Afghanistan but also requiring Bush to pull combat troops out of Iraq.

That bill calls for the troops to be out by next spring, rather than the fall as required in the House bill. Pelosi and Senate Majority Leader Harry Reid of Nevada both said they plan to work toward a compromise bill to bring to the president's desk.

Defense Secretary Robert M. Gates told reporters at the Pentagon on Thursday that the Army would consider curtailing or suspending home-station training of Reserve and National Guard forces and reduce funding for the repair of buildings and equipment if supplemental funding does not become law.