Senate Republicans today blocked a floor vote on a House-passed resolution that expresses disapproval of President Bush's plan to send thousands of additional U.S. troops to Iraq, as a procedural motion to cut off debate on the measure fell short of the 60 votes needed.

It was the second time this month that minority Republicans successfully filibustered a nonbinding resolution opposing the troop buildup.

Senators voted 56-34 to invoke cloture and proceed to a floor vote on the resolution, with seven Republicans joining all the chamber's Democrats in calling for an end to the debate. But the motion fell four votes short of the threshold needed under Senate rules.

Most Republicans objected to a rule barring amendments to the resolution and demanded a vote on a separate measure, introduced by Sen. Judd Gregg (R-N.H.), that pledges not to cut off funding for troops in the field.

The seven Republican senators who broke ranks with their colleagues and voted in favor of the cloture motion were John W. Warner (Va.), Chuck Hagel (Neb.), Norm Coleman (Minn.), Gordon Smith (Ore.), Olympia Snowe (Me.), Arlen Specter (Pa.) and Susan M. Collins (Me.). Warner is the former chairman of the Senate Armed Services Committee. He was a principal sponsor, along with Collins and Sen. Ben Nelson (D-Neb.), of a resolution that criticized the troop buildup and urged Bush to consider alternatives. That nonbinding resolution failed to pass the same procedural hurdle on Feb. 5.

One independent senator who caucuses with the Democrats, Joseph I. Lieberman (Conn.), joined 33 Republicans in opposing the cloture motion.

Ten senators -- nine Republicans and one Democrat who is ill -- did not vote today. Among those not present was Sen. John McCain (R-Ariz.), a contender for the Republican presidential nomination next year. He chose instead to continue a scheduled campaign visit to Iowa, where he called the Senate vote "meaningless." In a Des Moines news conference, he added, "It's insulting to the public and our soldiers to pretend we're discharging our responsibility in any meaningful way."

Several other senators who are in the running returned to Washington for the vote, including Hillary Rodham Clinton (D-N.Y.), who cut short an appearance in New Hampshire.

Besides McCain, another no-show was Sen. Jon Kyl (R-Ariz.), chairman of the Senate Republican Conference, who was leading an official trip to Iraq and the Middle East. In a statement issued by his office, he said the failed resolution would have set "a dangerous precedent by failing to guarantee funding for our troops in Iraq."

The Senate majority leader, Harry M. Reid (D-Nev.), urged colleagues before the vote to send a message to the White House: "not more war, but less war."

Despite the failure of the cloture motion, he said afterward the vote showed that "a majority of the United States Senate is against the escalation in Iraq."

Reid charged that by blocking the resolution today, most Republicans "wish to protect President Bush from an embarrassing vote." He described the GOP arguments as "diversions" intended to "turn the Senate into a procedural quagmire."

White House spokesman Tony Snow said in a statement that the voting in the House and Senate this week "gave the world a glimpse of democracy's vigor." Now, he said, Congress will turn to binding votes on funding Bush's supplemental funding request for the military.

"The president urges both Houses to approve his request," Snow said, adding that these next votes "should provide unmistakable assurance of this nation's resolve in achieving success, supporting the cause of democracy, and stopping terrorist forces in their ultimate aim of bringing their violence to our shores."

Today's Senate vote came a day after the House voted 246-182 to approve a nonbinding resolution that expresses support for U.S. forces but "disapproves" of Bush's Jan. 10 decision to send more than 20,000 additional combat troops to Iraq. It was that tightly worded resolution that was taken up in the Senate today.

In sometimes heated debate before today's vote, Republicans and Democrats sparred over the resolution, offering conflicting views on whether it actually supports the troops.

Republicans pointed to what they said was a contradiction in expressing support while denying the forces in Iraq the reinforcements they need to carry out a crucial Baghdad security operation. Democrats argued that the best way to show support for U.S. military personnel is to keep them out of sectarian strife between warring Iraqi factions and to take steps to bring them home.

Nelson, while saying he still prefers the resolution he co-sponsored with Warner and Collins, urged senators to "move beyond the debate about the debate" and hold a floor vote on the House-passed measure.

Sen. Lindsey O. Graham (R-S.C.) took aim at the House resolution and the rare Saturday Senate session that Reid called to consider it. "I would argue that we're not working," he said. "We're having a theatrical political debate that is doing more harm than good."

Graham, who favors a surge of U.S. troops into Iraq, as does McCain, challenged opponents of the buildup to show "the courage of their convictions" and vote to cut off funding for the war. He charged that no one wants to do that because they are not sure how it will play politically and they merely want to score points at Bush's expense with a nonbinding vote.

"The reason we are here on a Saturday playing stupid political games," Graham said, "is because our colleagues on the other side of the aisle are afraid to take a vote on cutting off funding." He also accused Democrats of blocking a vote on the Gregg resolution because they were afraid it would pass overwhelmingly and put Democratic presidential hopefuls in a bind with their party's left wing.

"If you believe this is a lost cause and victory can't be achieved, that our people are in the middle of a mess, a civil war, and not one person should get injured or killed because we've made huge mistakes that cannot be turned around, then cut off funding; have a vote on something that matters," Graham said. He added, "This political theater empowers our enemy and disheartens our own troops. And I think it is not worthy of the United States Senate's time."

Warner, a GOP stalwart who opposes the troop surge, said he voted against cutting off debate on his own resolution 12 days ago because he wanted "all colleagues to be heard," but that now "we must move forward." He said he supports Bush "on the diplomatic and economic aspects of his plan," but disagrees with him "on one basic point:" the need for 21,500 additional U.S. troops to "go into the streets and alleys of Baghdad to face an enemy fighting a sectarian war." Instead, he said, "it is the duty of the Iraqi armed forces . . . to take on the sectarian fight."

Gregg said he was confident that his resolution, if put to a vote, would "get significantly more than a supermajority in this body." He said in a floor speech, "I have a lot of frustrations about the war in Iraq. Everybody does around here. But we should not allow that frustration . . . to be taken out on the troops in the field." The House resolution's language -- expressing support for the troops but not their mission -- "truly is San Francisco sophistry," he said in an apparent reference to House Speaker Nancy Pelosi (D-Calif.), who represents San Francisco.

Sen. Carl M. Levin, the chairman of the Senate Armed Services Committee, blasted Bush and his surge plan, saying in a floor speech that instead of pressuring Iraqi leaders to settle their political differences, "the president would get us in deeper militarily." He also said the Iraqi leadership did not ask for more U.S. troops and that "this so-called surge" was an American idea.

"It may be called a surge, but I believe it is a plunge," Levin said, "a plunge into a sectarian caldron."

Supporters of the surge argue that the resolution opposing it "emboldens the enemy," Levin said, "but that is an extraordinarily naïve view of the enemy."

"What emboldens the sectarian fighters is the inability of Iraqi leaders to make the political compromises so essential to finally reining in the Sunni insurgents and the Shia militias," he said. "The enemy cares little what Congress says. It is emboldened by what the Iraqi leaders don't do. The enemy isn't emboldened by congressional debate. It is emboldened by open-ended occupation of a Muslim country by Western troops.

"The enemy is emboldened by years of blunders and bravado, false assumptions and wishful thinking, and ignorance of the history of the land being occupied. The enemy is emboldened by an administration which says it is changing course, which acknowledges that a political settlement by Iraqi leaders is essential to ending the violence, but then plunges us more deeply militarily into a sectarian witch's brew."

Sending in more U.S. troops , Levin said, "sends the false message that we can save the Iraqis from themselves."