The 52-47 vote fell short of the 60 votes needed to cut off debate under Senate rules. It was a sound defeat for Democrats who say the U.S. military campaign, in its fifth year and requiring 158,000 troops, cannot tame the sectarian violence in Iraq.
"The amendment tells our enemies when they can take over in Iraq," said Sen. Saxby Chambliss, a Republican.
The bill "is the wrong approach at the wrong time," he added.
The Senate debated the protracted war in Iraq in an all-night session. The speech-making marathon was in anticipation of Wednesday's vote on legislation that orders troop withdrawals within 120 days.
"We have to get us out of a middle of a civil war" said Sen. Joseph Biden. A political solution must be found "so when we leave Iraq, we don't just send our children home, we don't have to send our grandchildren back."
The legislation, initiated by Sens. Carl Levin and Jack Reed, both Democrats, would require President Bush to begin pulling troops out of Iraq in 120 days. After April 30, an unspecified number of troops would be allowed to remain in Iraq to fight terrorists, protect U.S. assets and train Iraqi security forces.
Before the vote, the Senate stopped for a prayer because as Democratic Majority Leader Harry Reid explained, "If there was ever a time for a prayer it would be before this very important vote," CBS News correspondent Bob Fuss reported.
Most senators got a chance for a few hours of sleep even while a handful of their colleagues took turns droning on through the night with floor speeches.
The "live" audience for the speeches was sparse, however, and there was no indication how aggressive the sergeant-at-arms was being in carrying out his official instructions to keep members near the chamber — or whether he was insisting that they be awake.
"It pretty much widened the partisan divide," CBS News chief Washington correspondent Bob Schieffer said of the debate, adding that Democrats and Republicans are "talking past each other."
With a half-dozen spectators watching from the gallery, Republican and Democrats were among those speaking during the night, including presidential candidates John McCain and Hillary Clinton.
"All we have achieved are remarkably similar newspaper accounts of our inflated sense of the drama of this display and our own temporary physical fatigue," said McCain, the top Republican on the Armed Services Committee.
Republicans were mostly unified in their opposition to setting a deadline for troop withdrawals, with a few exceptions. Three Republicans — Sens. Gordon Smith, Olympia Snowe and Chuck Hagel — announced previously they would support the measure.
Sen. Susan Collins, a Republican, who is up for re-election next year, also voted to advance the bill. Spokesman Kevin Kelley said Collins believes the measure should be subject to a simple majority vote and not the 60 votes needed to end parliamentary delaying tactics. Kelley said the senator still opposes the legislation.
Other Republican members, while uneasy about the war, said they could not support legislation that would force Mr. Bush to adhere to a firm pullout date.
Secretary of State Condoleezza Rice planned to spend most of Wednesday in Congress lobbying lawmakers on Mr. Bush's Iraq policy, a senior State Department official said.
Rice's plans included spending up to five hours in the morning and early afternoon in group and private meetings in both the Senate and House. The focus would be Iraq and other foreign policy issues, including the Middle East, the official said.
Among lawmakers scheduled to meet with Rice were Biden, Smith, Sen. John Warner, R-Va., and House Republican leader John Boehner of Ohio.
While the issue was momentous — a war more than four years in duration, costing more than 3,600 U.S. troops their lives as well as many thousands of Iraqis — the proceedings were thick with politics.
MoveOn.org, the anti-war group, announced plans for more than 130 events around the United States to coincide with the Senate debate, part of an effort to pressure Republicans into allowing a final vote on the legislation. A candlelight vigil and rally across the street from the Capitol building was prominent among them, with House leader, Speaker Nancy Pelosi, among those attending.