Repealing the US ban on gays and lesbians serving openly in the military by the end of 2010 now looks less likely.

Congress will begin a lame-duck session on Monday and the White House is pushing to repeal the law.

America’s largest gay rights group, Human Rights Campaign, is calling for grassroots action to urge the Senate to pass a defence bill with a repeal measure attached.

The annual National Defense Authorization Act has been passed by the House and the Senate Armed Services Committee with the repeal measure and must now be passed by the Senate.

The committee’s chairman, Senator Carl Levin, has been discussing with Republican Senator John McCain how the bill can proceed while it contains the repeal measure but Mr McCain is now demanding that it should be removed. He blocked a Senate vote on the matter in September.

Controversial measures may be removed from the bill to ensure it passes in the brief time window available.

The HRC is calling for campaigns in eight key states to persuade representatives to support the move.

HRC president Joe Solmonese said: “In the waning days of the 111th Congress, Senators have one last chance to follow the advice of the President and top military leaders by sending ‘Don’t Ask Don’t Tell’ to the dustbin of history.

“It would be a travesty for a small group of senators to continue to hold hostage a bill with critical military equipment and pay raises just because some senators don’t want to even debate repeal.”

Speaking to reporters at the weekend, Defence Secretary Robert Gates said he wanted to see the ban lifted this year but added: “I’m not sure what the prospects for that are.”

A Pentagon survey of troops on the effects of repealing the ban is to be released on December 1st. Sources said last month that the majority of those surveyed were open to the idea of serving alongside openly gay colleagues.

While President Obama and civilian officials support lifting the ban, many military leaders are understood to be opposed to making the change while the military is fighting two wars.

Last week, the 9th US Circuit Court of Appeals ruled that Don’t Ask, Don’t Tell should stay in place indefinitely after a US district judge ended the ban. The Republican gay group Log Cabin Republicans, which filed the original lawsuit, has appealed to the Supreme Court.