Only three Republicans -- Chuck Hagel of Nebraska, Gordon Smith or Oregon, and Olympia J. Snowe of Maine -- supported it. U.S. Sen. Susan Collins, a Maine Republican who voted for Levin-Reed in July, criticized Democratic leadership for refusing to seek compromise language to draw GOP moderates.

Three Democrats also defected: U.S. Sens. Ben Nelson of Nebraska and David Pryor of Arkansas, both moderates, and Christopher J. Dodd of Connecticut, a liberal candidate for president, who made clear that he does not think the Levin-Reed measure goes far enough.

Independent U.S. Sen. Joseph I. Lieberman voted against the Levin-Reed measure, as he has in the past.

The war amendments have been to the massive Pentagon spending and policy bill for fiscal year 2008.

After today's defeat, Reed said he and Levin will try to draw Republican support for their amendment with compromise language, perhaps seeking a non-binding goal rather than a hard deadline with the removal of most troops and the shift in mission from combat to training and support of Iraqi forces.

This week's big shift came Wednesday, when U.S. Sen. John W. Warner, R-Va., an influential voice on military affairs, surprised Democrats by voting against an amendment by U.S. Sen. Jim Webb, D-Va., that would have forced the Pentagon to give troops more time at home between deployment in Iraq.

The measure would have had the effect of restricting the Pentagon's ability to maintain current force levels in Iraq. The Webb amendment died on a 52-to-47 vote on a procedural question that needed 60 votes to prevail.

Yesterday, Democrats -- including Rhode Island's two senators -- split on an amendment by Sen. Russ Feingold, D-Wis., that would have forced a complete U.S. withdrawal from Iraq by next July 1, cutting off funding for the war at that point.

Fellow Rhode Island Sen. Sheldon Whitehouse supported the amendment, as he had earlier this year. Reed again opposed it, one of 20 Democrats to do so. ``I want to bring the troops home,'' he said, but called the Feingold measure ``just too restrictive'' because it could cut logistical and training fund that should continue after the bulk of U.S. forces leave Iraq.

After the vote today, Whitehouse issued a statement, saying Reed's amendment "would have set a smart, responsible strategy to safely redeploy American troops – but once again, the Republican minority in the Senate has used Senate rules to block the way.

“We face a simple question: is it in the long-term best interests of our nation for American troops to remain in Iraq? Americans have overwhelmingly answered no. I will keep fighting to bring our troops home safely, and bring them home soon.”

Reed said he still holds out hope for a vote next week on a compromise version of his measure that would command more Republican support and begin to chart a bipartisan course for concluding the war.