"We must heed the results of the November elections and the wishes of the American people," said Majority Leader Harry Reid.

Reid, D-Nev., spoke moments before a vote that sidetracked a nonbinding measure expressing disagreement with Bush's plan to deploy an additional 21,500 troops to Iraq.

The vote was 49-47, or 11 short of the 60 needed to go ahead with debate, and left the fate of the measure uncertain.

Senate Republican Leader Mitch McConnell of Kentucky described the test vote as merely a "bump in the road" and added that GOP lawmakers "welcome the debate and are happy to have it."

The political jockeying unfolded as Democrats sought passage of a measure, supported by Sen. John Warner, R-Va., that is critical of the administration's new Iraq policy. It was the first time Democrats had scheduled a sustained debate on the war since they won control over Congress in last fall's midterm elections.

McConnell called for equal treatment for an alternative measure, backed by Sen. Judd Gregg, R-N.H., saying Congress should neither cut nor eliminate funding for troops in the field. That measure takes no position on the war or the president's decision to deploy additional forces.

Democrats launched a withering attack on Bush's war policy in the run-up to the vote.

"The American people do not support escalation. Last November, voters made it clear they want a change of course, not more of the same," said Reid. "The president must hear from Congress, so he knows he stands in the wrong place, alone."

Sen. Dick Durbin of Illinois, the second-ranking Democrat, echoed Reid. "If the Republicans want to stand by their president and his policy, they shouldn't run from this debate. If they believe we should send thousands of our young soldiers into the maws of this wretched civil war, they should at least have the courage to stand and defend their position," he said.

The war has claimed the lives of more than 3,000 U.S. military personnel so far, and costs are counted in the hundreds of billions of dollars. The administration in recent days asked Congress for $245 billion more to cover the costs of the conflict through 2008.

In Baghdad on Monday, there were signs that the much-awaited operation to restore peace to the capital is gearing up nearly a month after it was announced. Iraqi troops manned a major new checkpoint at the northern gate to Baghdad, and Lt. Gen. Abboud Gambar, who will direct the operation, took charge of his still-unfinished command center.

But bombings and mortar attacks killed at least 74 people Monday across Iraq ¡ª all but seven of them in Baghdad. Nearly 1,000 people have been killed in attacks in the past week.

Before the Senate test vote, McConnell sought to deflect charges that Republicans were hoping to block a debate. He said the roll call was meaningless, a "bump in the road" required to settle a procedural problem.

But behind the procedural quarrel lay uncertainty about the verdict the Senate would ultimately reach on Bush's decision to send 21,500 additional troops.

Democrats hoped to gain enough Republican votes to pass the measure expressing disagreement with Bush's decision, and to send the commander in chief an extraordinary wartime rebuke on a bipartisan vote.

It was an outcome that the White House and Senate Republican leadership hoped to avoid. They concentrated on a relatively small number of swing votes, many of them belonging to GOP senators expected to be on the ballot in 2008.

Gregg's alternative said Congress should not take "any action that will endanger United States military forces in the field, including the elimination or reduction of funds for troops in the field, as such an action with respect to funding would undermine their safety or harm their effectiveness in pursuing their assigned missions."

The measure advanced by Democrats and Warner said the same thing, but it also says the Senate "disagrees with the `plan' to augment our forces by 21,500 and urges the president instead to consider all options and alternatives."

Republicans and Democrats carried out their clash as 10 members of "Code Pink, "an anti-war group, were arrested and charged with disorderly conduct during a protest in front of Sen. John McCain's office in a building across the street from the Capitol. "They were absolutely compliant, peaceful," Sgt. Kimberly Schneider said of the protesters.

McCain, a likely Republican presidential candidate, opposes the measure expressing disagreement with the increase in troops.