America’s largest gay rights organisation, Human Rights Campaign, is backing President Barack Obama for re-election in 2012.

HRC leader Joe Solmonese said that Obama was the only clear choice for the LGBT vote next year.

In an article for Advocate.com, Mr Solmonese called the president an “unwavering ally” who has “delivered on promises both great and small”.

Last year, Obama was strongly criticised by gay rights campaigners who felt he was slow to act on the ban on openly gay troops.

In 2008, he voiced support for civil unions but added: “Marriage is between a man and a woman.” In December, he said his position on gay marriage was “constantly evolving” and that he would “continue to wrestle with” it.

Mr Solmonese wrote that Obama’s greatest achievement had been to repeal the military’s gay ban, but praised other initiatives, such as the Matthew Shepard and James Byrd Jr Hate Crimes Prevention Act and policies to ensure Medicaid or Medicare hospitals accept gay couples.

He added: “With all of our success, much remains to be done, which is why the Human Rights Campaign has endorsed President Barack Obama’s re-election campaign. Our endorsement now will allow HRC along with our community and our allies to fully mobilise around what will be a difficult but critically important campaign.

“One need not look further than the records of the other candidates for a wake-up call about how important this election will be to LGBT people. As the fight for equality moves forward, President Obama is marching with us, while the alternatives would stop us in our tracks.

“It’s a long time between now and November 2012, but the president has and continues to stand up for our community. We owe it to ourselves and our future to stand up with him again, starting now.”

Next year’s presidential race will include the first openly gay candidate – Republican Fred Karger.

Mr Karger, who has not shied away from discussing sexual orientation, has years of experience in the Reagan and Bush senior campaign teams.

However, analysts predict he has a very slim chance of success.