WASHINGTON - A Democratic plan to require the withdrawal of U.S. combat troops from Iraq passed its first test in the House Appropriations Committee on Thursday as the panel voted to go ahead, overcoming Republican opposition.

Members voted 37-27 to uphold a provision in a $124 billion war spending legislation that calls for troops to leave Iraq before September 2008, and possibly sooner if the Iraqi government does not meet certain benchmarks. Republicans had proposed stripping out the timetable.

The vote gave Democrats a victory, if only for the moment, in their effort to challenge President Bush's war policies and pressure him into starting a withdrawal of U.S. troops.

The committee was expected to approve the overall spending bill by later Thursday, but its longer-range fate is dim. In the Senate, minority Republicans can use procedural moves to block the troop withdrawal language and the White House has threatened to veto the bill if it contains the language forcing the removal of troops.

Rallying enough support for the bill, which allots $95.5 billion for the wars in Iraq and Afghanistan, has been a challenge for Democratic leaders. Many party members support bringing troops home sooner than the 2008 deadline, while others have been reluctant to embrace a firm deadline to end the war.

Republicans proposed eliminating the 2008 deadline and inserting language that would promise not to cut funding for troops.

"We are trying to end the authorization of the war if the Iraqis and the administration don't perform," said Rep. David Obey, D-Wis., committee chairman.

"Either you're going to provide for our troops or you're not," said Rep. Jerry Lewis, R-Calif., the panel's top Republican.

"Nobody wants our troops out of Iraq more than I do" but "we can't afford to turn over Iraq to al-Qaida," said Rep. C.W. Bill Young, the ranking member on the subcommittee that oversees military spending.

But Democrats said the timetable was necessary to force the Iraqis to step up, and proposed a provision promising to "fully support the needs" of service members in combat. Republicans said the amendment by Rep. John Murtha, D-Pa., did not go far enough to protect funding for the war, but it passed 37-27.

"I want this war to end. I don't want to go to any more funerals," said New York Rep. Rep. Jose Serrano as the House Appropriations Committee debated the measure, expected to pass on a near party-line vote by day's end.

Young, R-Fla., proposed a separate amendment that would have restricted funding to steps needed to carry out a troop withdrawal. He said he would vote against it, but said it was an issue that should be settled.

Obey called it a poison pill, and urged Democrats to reject it, as well.

The proposal failed unanimously on a vote of 64-0.

Republicans accused Democrats of micromanaging the war, taking over a role best left to the generals. Rep. Hal Rogers of Kentucky accused Democrats of an "ill-advised and precipitous withdrawal" plan. And Rep. Roger Wicker of Miss., said the legislation was a backdoor method of cutting off funds for the troops -- a charge that the Democratic chairman, Rep. David Obey of Wisconsin, swiftly disputed.

Obey and the Democratic leadership hoped for a final vote by late in the day on the measure, which includes $95.5 billion in funds for the wars in Iraq and Afghanistan.

The political landscape was different across the Capitol, where Republicans expressed confidence they had the votes to defeat an alternative approach advanced by Majority Leader Harry Reid and Senate Democrats.

Their proposal sets a goal of a troop withdrawal by March 31, 2008. A mid-afternoon vote was expected.

The Iraq debate spilled over to the 2008 campaign for the White House.

Sen. Hillary Rodham Clinton, a Democratic presidential candidate, said in a New York Times interview that if elected she would maintain a scaled-down American military force in Iraq that would stay off the streets in Baghdad and no longer would try to protect Iraqis from sectarian violence.

She cited "remaining vital national security interests" for a continued deployment of U.S. troops in Iraq aimed at fighting al-Qaida, deterring Iran, protecting Kurds and possibly supporting the Iraqi military, the newspaper reported Wednesday night on its Web site.

She said her plan was consistent with the Senate resolution, saying it called for "a limited number" of troops to stay in Iraq to protect the U.S. Embassy and other personnel, train and equip Iraqi forces and conduct "targeted counterterrorism operations."

While the House bill is unlikely to sail through unchecked, Democrats say its passage -- even if by a slim majority -- would be a loud message to the president to end the war. Pelosi was trying to line up votes from party liberals who want troops out of Iraq sooner than the 2008 deadline, as well as more conservative Democrats who are concerned the bill would micromanage the war.

A total of 10 peaceful anti-war protesters were arrested, both inside the committee room and outside the building where the debate was unfolding.

Sgt. Kimberly Schneider of the Capitol Police said they would be charged with unlawful assembly and disorderly conduct. "They were being loud and boisterous. They were told to stop and they didn't so they were arrested," she said.