WASHINGTON - A defiant, Democratic-controlled Senate approved legislation Thursday calling for the withdrawal of U.S. combat troops from Iraq within a year, propelling Congress closer to an epic, wartime veto confrontation with President Bush.

The 51-47 vote was largely along party lines, and like the House's passage of a separate, more sweeping challenge to the administration's war policies a week ago, fell far short of the two-thirds margin needed to overturn the president's threatened veto. It came not long after Bush and House Republicans made a show of unity at the White House.

“With passage of this bill, the Senate sends a clear message to the president that we must take the war in Iraq in a new direction. Setting a goal for getting most of our troops out of Iraq is not - not, not - cutting and running,” said Sen. Robert C. Byrd, D-W.Va., shortly before the vote. Passage cleared the way for negotiations on a compromise with the House.

Senate Republican leader Mitch McConnell of Kentucky rebutted quickly. “Nothing good can come from this bill,” he said. “It's loaded with pork that has no relation to our efforts in Iraq and Afghanistan, and it includes a deadline for evacuation that amounts to sending a ‘Save the Date' card to al-Qaida.”

Several blocks away, the commander in chief stood with Republican House members and told reporters they were united. “We expect there to be no strings on our commanders and that we expect the Congress to be wise about how they spend the people's money,” he said.

In private, Bush was at least as emphatic, according to participants at a closed-door session in the White House East Room with the GOP rank and file. “He said he will veto a bill that comes to his desk with too many strings attached or too much spending,” said one official in attendance.

While both sides have spoken positively about a need for compromise, there also was strong political pressure within both parties for a veto fight.

Democrats are under pressure to challenge Bush on the war following their victories in last fall's elections. At the same time, Republicans say Bush will blame anti-war lawmakers if money begins to run short for the troops in the field.

The House-passed measure requires the withdrawal of combat troops by Sept. 1, 2008. The Senate bill mandates the beginning of a withdrawal within 120 days, and sets a goal of March 2008, for its completion.

There was no suspense in the Senate's vote, following a test earlier this week in which Republicans had sought to strip out the nonbinding timeline for a troop withdrawal. There were 48 Democrats and two Republicans, Chuck Hagel of Nebraska and Gordon Smith of Oregon, voting for the measure, along with Sen. Bernie Sanders, a Vermont independent. Among the supporters, only Sen. Mark Pryor, D-Ark., had voted to jettison the timeline earlier in the week.

The votes in opposition were cast by 46 Republicans and Sen. Joseph Lieberman of Connecticut, an independent Democrat.