The vote was 93-6 to shelve the proposal, which would have allowed "only forces that are critical to completing the mission of standing up Iraqi security forces" to remain in 2007.
The vote came alongside a daylong debate in the House, where Republicans defended the war as key to winning the global struggle against terrorism while Democrats excoriated President Bush and his policies.
"We must stand firm in our commitment to fight terrorism and the evil it inflicts throughout the world. We must renew our resolve that the actions of evildoers will not dictate American policy," House Speaker Dennis Hastert, R-Ill., said in remarks laden with references to the Sept. 11, 2001, terrorist attacks.
The war was "a grotesque mistake," countered the Democratic leader, Rep. Nancy Pelosi of California. "The administration continues to dig a hole. They refuse to come up and see the light," she said.
Choreographed by the GOP, the debate unfolded four months before midterm elections that will decide the control of Congress. The administration, for its part, was so determined to get its message out that the Pentagon distributed a highly unusual "debate prep book" filled with ready-made answers for criticism of the war.
Partisan lines were drawn quickly.
"Is it al Qaeda or is it America? Let the voters take note of this debate," said Republican Rep. Charles Norwood of Georgia, attacking war critics as defeatists who do not deserve re-election.
Countered Rep. Carolyn Kilpatrick, D-Mich.: "America, listen. Look. Should we stay the course or should we have a plan of redeployment to protect our troops and to protect America?"
The United States has absorbed the deaths of 2,500 troops in the three-year conflict, which began when a U.S.-led invasion toppled Saddam Hussein, but quickly turned sour in the face of a brutal insurgency.
Reacting to the new milestone on combat deaths, White House press secretary Tony Snow said, "It's a number." He said that Mr. Bush "feels very deeply the pain that the families feel." As the updated death toll was announced at the Pentagon, the House and Senate held moments of silence.
Polls show the war has become unpopular. But Mr. Bush has tried to rally support in the days since the death of terror leader Abu Musab al-Zarqawi, and the recent completion of a new Iraqi government.
The Pentagon's 74-page battle plan for the debate says that "Iraq will become a haven for terrorists, murderers and thugs," if the United States leaves "before the job is done."
"We cannot cut and run," it says at another point, anticipating Democratic calls for a troop withdrawal on a fixed timetable.
The Associated Press obtained a copy of the document. It was sent to both Republicans and Democrats and it laid out the administration's positions in strong terms and offered page after page of counterpoints to criticisms that Democrats typically level against Mr. Bush's war policies.