WASHINGTON, Feb. 5 — Republicans late this afternoon blocked a potentially momentous Senate debate, at least for now, on a bipartisan resolution opposing President Bush’s troop buildup in Iraq.
Forty-nine senators, almost all Democrats, voted to proceed with the debate, 11 short of the number needed under Senate rules on the issue. Forty-seven senators, nearly all Republicans, voted not to proceed.
This afternoon’s result cast doubt on whether the Senate would move toward a vote on what lawmakers of both parties described as the paramount issue of the day. Now it appears certain that more negotiations will take place on what war-related measure, if any, will be voted upon.
If 60 “yes” votes had materialized today, the Senate would have opened debate on a resolution sponsored by Senators John W. Warner, Republican of Virginia, and Carl Levin, Democrat of Michigan, that opposes the president’s plan to add about 21,500 troops to the American force in Iraq.
Senator Joseph I. Lieberman, independent of Connecticut, urged his colleagues to vote “no” today, asserting that a debate on the Warner-Levin resolution would hurt the morale of American troops and embolden their enemies.
“What will it say to our soldiers?” he asked.
But Senator Chuck Hagel, Republican of Nebraska, rejected the notion that a debate would be harmful. The senator said he would have welcomed a debate on the war in Vietnam, four decades ago when he fought and was wounded there, instead of the Congress “just going along” with the conflict.
With Democrats refusing to allow votes on two Republican-backed alternatives, leaders from both parties were locked in a showdown that would prevent the Senate from beginning consideration of the resolution, which has been in the works for weeks and declares Senate disagreement with the troop buildup.
The Democrats were refusing a demand by Senator Mitch McConnell of Kentucky, the Republican leader, for votes on two alternatives — one that would set 11 conditions for the Iraqi government if it wanted to retain American support and a second declaring that Congress should not cut off any spending for the troops.
That second alternative, authored by Senator Judd Gregg, Republican of New Hampshire, was proving problematic for Democrats since it was likely to garner a substantial amount of support and potentially be the resolution capable of winning the 60 votes that Republicans say should be a threshold for passage.
“There is nothing the minority is asking for here that is extraordinary,” Mr. McConnell said.
But Democrats said Republicans were running interference for the White House to avoid what is essentially a vote of “no confidence” in Mr. Bush.
“We are witnessing the spectacle of a White House and Republican senators unwilling even to engage in a debate on a war that claims at least one American life every day and at least $2.5 billion dollars a week,” said Senator Richard J. Durbin of Illinois, the No. 2 Democrat.
The Republican approach could backfire if Democrats are able to persuade the public that the president’s allies are stonewalling in the Senate. But at the moment, the Republicans are united, including Mr. Warner, providing some credibility for the claim that Democrats are not granting Republicans a fair hearing on their alternatives.