|Obama has come under pressure from civil rights activists to fulfil his campaign promise [EPA]
A White House backed bid to end the ban against gays serving openly in the US military cleared a major procedural hurdle in the country's Senate on Saturday, meaning the law is all but guaranteed to pass.
Supporters mustered more than the needed 60 votes in the 100-member Senate. There were 63 votes in favour and 33 against limiting debate on the legislation to lift the 17 year old "don't ask, don't tell" policy.
The Senate is expected to give it final congressional approval as early as Sunday, clearing the way for President Barack Obama to sign it into law.
The House of Representatives voted to repeal the policy earlier in the week.
"The Senate has taken an historic step toward ending a policy that undermines our national security while violating the very ideals that our brave men and women in uniform risk their lives to defend," Obama said in a statement on Saturday.
"By ending 'Don't Ask, Don't Tell,' no longer will our nation be denied the service of thousands of patriotic Americans forced to leave the military, despite years of exemplary performance, because they happen to be gay. And no longer will many thousands more be asked to live a lie in order to serve the country they love," he said.
Obama vowed during his 2008 presidential campaign to end the ban, which he denounced as unfair, unwise and a violation of basic human rights. He had been facing criticism from left-wing groups who said he failed to push hard enough to end the policy.
At least 13,000 men and women have been expelled from the US military under "don't ask, don't tell," which allows gays to serve in the armed forces as long as they keep their sexual orientation secret.
Defense Secretary Robert Gates and other supporters of the repeal argued it would allow for a more orderly transition for the military than would occur if it was delayed until the likely court-ordered end to the policy.
Once it is enacted into law, as anticipated, the Pentagon will have an undetermined amount of time - possibly months - to educate service members and prepare for the policy change before it is ready to 'certify' the repeal.
When the repeal is certified, there will be another 60 day period before the new policy of allowing gays to openly serve takes effect. Until that time "don't ask don't tell" is still in effect.
"The only method of repeal that places the timing of the repeal and control of implementation in the hands of the military leaders is enactment of this bill," Senator Carl Levin, chairman of the Senate Armed Services Committee, said.
Opponents of gays serving openly in the military argue that lifting the ban would undermine order and discipline and harm unit cohesiveness, especially among combat troops.
Republican opposition has been largely led by Obama's 2008 challenger for the presidency, John McCain, a former Navy pilot and prisoner of war in Vietnam.
McCain said it may be too early to end the ban and challenged a recent Pentagon study that predicted there would be little impact if the policy were lifted. In a Senate speech, he argued against imposing a change while the country is at war.
"This debate is not about the broader social issues that are being discussed in our society, but what is in the best interest of our military at a time of war," McCain said.
Those favouring repeal contend the ban is discriminatory, denies the military needed soldiers and, in Obama's words, "violates fundamental American principles of fairness."
While Gates and Admiral Mike Mullen, chairman of the military's Joint Chiefs of Staff, advocate repeal, there has been uneven support in the military.
Marine Corps Commandant James Amos, for instance, has warned that ending the policy could be dangerous while the United States is fighting wars in Iraq and Afghanistan.
The policy, which began in 1993 at the request of then-Democratic President Bill Clinton, has faced increased court challenges in recent years.
A federal judge in California in October imposed an injunction against enforcement of the ban, ruling it a violation of free-speech and due-process rights.
But the following week, a federal appeals court ruled that the Pentagon could reinstate the policy, pending further court action.