Rights groups say the "Don't Ask, Don't Tell" policy infringes on the rights of homosexuals in the army [AFP]

The US Senate has blocked a bid to lift a ban on gays from serving openly in the military.

Democratic supporters of repealing the "Don't Ask, Don't Tell" policy -  brought in as compromise to resolve the issue of gays in the military in 1993 -  ran against a wall of Republican resistance.

A total of 56 senators to 43 voted to advance debate on the annual Pentagon military spending bill to which the repeal of the gays ban had been attached, falling four short of the 60 votes on Tuesday, needed to move forward.

"We're disappointed at not being able to proceed to the legislation, but we'll keep trying," White House spokesman Robert Gibbs said after Democratic senators Mark Pryor and Blanche Lincoln also voted against.

"I think you have in the defense bill obviously very important funding for the priorities of our Pentagon and our troops," Gibbs added.

Less than two months before November mid-term elections, polls show overwhelming US public support for ending the policy which requires members of the military to hide their homosexuality or be dismissed.

Opposition

Critics say the ban infringes on civil rights of gay military personnel and has harmed US national security by forcing out some 14,000 qualified troops.

But a top general told politicians that a Pentagon survey showed US marines were predominantly opposed to lifting the ban.

"I've heard at the Marine bases and the Marine input for the online survey has been predominantly negative," General James Amos told the Senate Armed Services Committee in written testimony.

Amos, who has been tapped to take over as the head of the Marines, also said he opposed changing the law, which he described as a "reasonable" compromise.

"I'm concerned that a change now will serve as a distraction to Marines who are tightly focused at this point on combat operations in Afghanistan," Amos wrote.