WASHINGTON - The Senate on Thursday blocked a bid to repeal the "don't ask, don't tell" policy toward gays in the military, a vote likely to doom the effort this year.

The 57-40 vote to cut off a Republican-led filibuster, or extended debate, fell three votes short of what Senate rules require. Sen. Susan Collins (R., Maine) joined 56 Democrats to vote yes, while 39 Republicans and Sen. Joe Manchin (D., W.Va.) voted no. All Philadelphia-area senators voted in favor of ending the filibuster.

Senate Majority Leader Harry Reid (D., Nev.) was thwarted by the objections of some Republicans who oppose lifting the ban while the country is fighting two wars. Other Republican senators felt bound by a pledge to their leaders not to vote on anything unrelated to tax cuts or this year's budget until those matters are resolved.

While Thursday's vote wasn't strictly on the merits of repealing the policy, reconsideration is highly unlikely this year because of limited time and the Senate's full agenda of tax cuts, government funding, and perhaps the New START nuclear arms treaty. Senators hope to conclude the 111th Congress at the end of next week.

Repeal supporters vowed to keep fighting, citing how close advocates of ending the 17-year-old policy came, and realizing that in the 112th Congress that convenes in January, Republicans will control the House of Representatives and Democrats will have five fewer Senate seats, down to 53.

Reid's frustration was palpable as he made a last-ditch appeal to colleagues to end the policy.

"The theory behind 'don't ask, don't tell' is a thing of the past, and we should put the policy behind us too. It's obsolete. It's embarrassing. It weakens our military, and it offends the very values we ask our troops to defend," he said.

"I have bent over backwards to find a way to get this bill done. But it is clear that Republicans - led by a couple of senators who simply do not want to have a vote on repealing 'don't ask, don't tell' - are doing everything they can to stand in the way," Reid said.

Core values

Sen. Ben Nelson (D., Neb.) said: "The issue is not whether to allow gay people to serve in the military, but whether we ask them to lie. Asking them to lie undermines the core values of our military - honesty, integrity and trust. When those values are undermined anywhere, they are undermined everywhere."

The repeal was part of a bill to authorize defense spending in fiscal 2010, which began on Oct. 1. The Pentagon has been funded on a stopgap basis so far.

Traditionally, such defense measures win bipartisan approval - for 48 straight years, Congress has approved the legislation.

Not this year. The entire bill is now stalled.

"I am extremely disappointed that yet another filibuster has prevented the Senate from moving forward," President Obama said in a statement.

"A minority of senators were willing to block this important legislation largely because they oppose the repeal of 'don't ask, don't tell.' As commander in chief, I have pledged to repeal this discriminatory law. . . . This law weakens our national security, diminishes our military readiness, and violates fundamental American principles of fairness, integrity and equality," Obama said.

The House voted to end the ban earlier this year.

Repeal supporters thought that they finally had gotten their elusive Senate momentum after the Pentagon last week released the results of an eight-month study. More than 115,000 military personnel were surveyed, and 70 percent said that ending the ban on gays and lesbians serving openly would have a positive or neutral effect.

However, the survey also found that a sizable minority would oppose repeal, saying that serving alongside openly gay and lesbian soldiers could affect their morale, training, unit cohesion, and even whether they would stay in the military.

Mixed messages

Congress received mixed messages from the military leadership about whether to repeal the law. Defense Secretary Robert M. Gates and Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, urged Congress to repeal the law.

They noted that the courts are increasingly ruling on the issue and could force the military to repeal suddenly, before the military could properly prepare for the change.

At the same time, chiefs of individual military services told Congress that they oppose a repeal now, because of the two wars.

Sen. John McCain of Arizona, the top Republican on the Armed Services Committee, was unconvinced of the need for repeal. The former Navy pilot and Vietnam prisoner of war thought the survey's response rate of 28 percent was low, and that the closer troops got to combat, the more resistance they offered to repeal.