March 27 (Bloomberg) -- The Senate backed a Democratic proposal calling for the withdrawal of U.S. troops from Iraq, hours after the Bush administration warned it would spur a veto.

The Senate voted to keep the provision in a $122 billion emergency spending measure that funds the wars in Iraq and Afghanistan. A Republican bid to eliminate the timeline failed 50-48.

The administration said today that President George W. Bush would veto any legislation that includes a withdrawal timetable.

The proposal calls for U.S. troop withdrawals from Iraq to begin 120 days after final passage of the measure, with a goal of having almost all forces withdrawn by March 31, 2008. Some troops would remain to train Iraqi forces, pursue terrorists and protect U.S. diplomatic sites.

``Our troops have done everything we asked them to do and now it is time to start bringing them home,'' Washington Democrat Patty Murray said. ``The conflict in Iraq is not going to be solved by military force alone. It is going to require a political solution.''

More than 3,100 U.S. military personnel have died in the war since Bush ordered an invasion in March 2003 to overthrow Saddam Hussein's regime.

Senate Republican leader Mitch McConnell said setting a withdrawal timeline aids America's enemies.

``Announcing a surrender date is certainly not in our national interest,'' he said.

House Measure

The House last week voted to approve a $124 billion spending measure that would require most of the 141,000 U.S. troops in Iraq to pull out by September 2008. The Senate legislation, expected to be passed later this week, would have to be reconciled with the House version before being sent to Bush.

Democrats conceded they do not have enough support in either chamber to override Bush's expected veto. After the vote today, they said they are trying to increase the political pressure on Bush to change course.

``This is not one battle, it's a long-term campaign to persuade the president, to pressure the president, to change course,'' New York Democrat Chuck Schumer said.

Switched Votes

Last week, the Senate defeated the withdrawal timetable as a stand-alone measure by a vote of 50-48. It passed today because two senators switched sides: Democrat Ben Nelson and Republican Chuck Hagel, both of Nebraska.

Hagel, a frequent critic of the war, said the provision sets a ``goal'' for a U.S. withdrawal from Iraq, not a ``binding date.'' Nelson said he decided to back the measure because it sets out benchmarks for the Iraq government to meet and regular briefings for Congress.

``Setting measurable goals is absolutely essential for our strategy in Iraq,'' he said.

Before final passage, Senators are likely to consider additional amendments including a requirement that Bush seek congressional approval before taking any military action in Iraq.

To contact the reporter on this story: Nicholas Johnston in Washington at njohnston3@bloomberg.net;

Last Updated: March 27, 2007 19:09 EDT