WASHINGTON (AP) - Senate Democrats have drafted a $121.5 billion war spending bill that would direct President George W. Bush to begin bringing home troops from Iraq with the goal of ending U.S. combat missions there in just over a year.

The provision is similar to a resolution the Senate narrowly rejected last week. It failed on a 50-48 vote, falling 12 votes shy of the 60 needed to pass, after Bush vowed to veto the legislation.

But unlike that resolution, Democrats think the spending legislation has a much better chance of passing. Sen. Ben Nelson, a Democrat who voted against last week's resolution, has agreed to support the spending legislation because it includes a provision he wants outlining benchmarks for the Iraqi government.

"United States troops should not be policing a civil war, and the current conflict in Iraq requires principally a political solution," states a copy of the draft bill, obtained by The Associated Press. Like the bill the Senate defeated, it would set a nonbinding goal of pulling out combat troops by March 31, 2008.

Senate Appropriations Committee Chairman Robert Byrd, a Democrat, released details to panel members Wednesday in anticipation of a committee vote on the bill on Thursday.

Republicans are expected to bristle at the inclusion of the Iraq policy provision. The measure would require Bush to begin removing U.S. combat troops within four months of the bill's passage.

"We must not risk providing our troops the equipment and supplies they need to carry out their mission by including this risky Democratic leadership retreat plan, this poison pill," said Senate Republican Leader Mitch McConnell. "We owe our troops better than that."

The House of Representatives is expected to vote Thursday on a similar $124 billion spending bill that would finance the wars in Iraq and Afghanistan. The House bill, which Bush also threatened to veto, would demand that combat troops be out of Iraq before September 2008, possibly sooner.

The leader of the House, Nancy Pelosi, continued Wednesday to press party members to back the bill, unsure whether she had enough votes to pass it. In a closed-door meeting, President Jimmy Carter's national security adviser, Zbigniew Brzezinski, tried to persuade party skeptics that the bill was their best chance at ending the politically unpopular war.

Max Cleland, a Vietnam War veteran and former Democratic senato, also came out in support of the bill, a name that could help to persuade more conservative Democrats who do not want to tie the hands of military commanders.

Most Republicans say they oppose setting hard-and-fast deadlines to end the war because it would tie the hands of military commanders and embolden insurgents to ramp up attacks once U.S. troops are gone.

But some Republicans might have a tough time turning the proposal down because it is attached to a bill that provides much-needed funding for troops in combat, assistance for fishers and farmers, hurricane reconstruction and other popular spending projects.

Byrd's bill would leave an unspecified number of troops behind in Iraq for anti-terrorism missions, to train Iraqi forces and to protect coalition infrastructure and personnel. Of the more than 140,000 U.S. troops in Iraq, fewer than half are combat forces.

The Senate proposal also would urge the Iraqi government to meet certain benchmarks, such as disarming militias and amending the constitution to protect Sunni minorities.