WASHINGTON (AFP) - Mr Erwin de Leon married a United States citizen nearly three years ago, but the Filipino is still in immigration limbo for one simple reason - his spouse is a man.

Mr De Leon and his husband John Beddingfield, the rector at an Episcopal church in Washington, were wed in the US capital which, like nine states, has legalised same-sex marriages.

But the federal government does not recognise such unions, so as far as it is concerned, the pair might as well be roommates.

Now they are counting on President Barack Obama and his pledge to pursue immigration reform to obtain, finally, legal permanent residency for Mr de Leon.

"There's still no security. The reality is I'm still seen as a foreign national, as a foreign student, even if I've been here for quite some time and I consider myself an American through and through," said Mr de Leon, who is 46.

"I know a few people who came here in 1990, the same year, and have now been citizens for some time.

"I know of people who came way after me who've become citizens. So it's rather frustrating, because for me, I can't wait for the day where I can be a full citizen and vote."

He and Mr Beddingfield, 48, have been together for 14 years.

They formalised their relationship with a domestic partnership in 2003, and were legally wed in April 2010, the month after Washington began allowing same-sex marriages.

Mr De Leon first came to the United States on a student visa to pursue his doctoral degree. He has repeatedly renewed various temporary visas and is looking for an employer to sponsor him for a residency permit.

If he had married a woman, she could have sponsored him for a green card immediately, and within three to five years, for citizenship.

However, for Mr de Leon, his marriage to Mr Beddingfield doesn't exist for immigration purposes.

Nevertheless, Mr de Leon says he sees "a light at the end of my tunnel."

In May 2012, Mr Obama voiced support for same-sex marriage, giving gay couples hope they will gain the same immigration rights as heterosexual couples - as is the case in more than 20 countries including France, Germany and Britain.

The heart of the battle, however, lies beyond the president's control.

In Congress, Democrats and Republicans are in negotiations over an ambitious overhaul of the immigration system, which could lead to a pathway to legal residency and even citizenship for some of the 11.5 million people currently living in the US without papers.

A fragile consensus has formed around a basic principle: give papers to those who came to the US as children and those who have never broken the law.

But many Democrats and some Republicans also want reforms to include same-sex couples, including, under one proposal, to create an immigration category called "permanent partners."

That could be a way to recognise same-sex unions in immigration while side-stepping the Defence of Marriage Act, the 1996 federal law that defines marriage exclusively as a union between a man and a woman.

"The so-called Defence of Marriage Act forces many Americans to choose between the country they love and being with the people they love. This destructive policy tears families apart," said Senator Patrick Leahy.

Mr Leahy, a Democrat from Vermont, and Republican Senator Susan Collins from Maine are co-sponsors for a bill supporting immigration rights for same-sex couples.

But many other Republicans - the minority party in the Senate, but the majority in the House of Representatives - consider the issue secondary and distracting.

"Which is more important: LGBT (rights) or border security?" Republican Senator John McCain said recently.

"I'll tell you what my priorities are. If you're going to load it up with social issues, that is the best way to derail it, in my view."

Another Republican senator, Ms Lindsey Graham, asked sarcastically, "Why don't we just put legalized abortion in there and round it all out?"

The other hope lies with the Supreme Court, which will decide in June on the constitutionality of DOMA, and could in theory force the federal government to recognise gay marriage.

Like many bi-national, homosexual couples, Mr Rodrigo Martinez and Mr Edwin Echegoyen have been watching the debates carefully.

The pair, who have been together for a decade, have just celebrated their second wedding anniversary.

But their wedded bliss is marred by serious legal battles aimed at keeping Mr Martinez, from El Salvador, from being deported - which have cost them around US$38,000 (S$47,300).

A judge has granted Mr Martinez, 34, a reprieve - a temporary work permit while he awaits a decision on his second application for a green card.

Mr Martinez and Mr Echegoyen, 44, hope that when the time comes, Mr Obama will have succeeded in convincing lawmakers that, as the president said in a recent interview, same-sex couples "should not be treated differently when it comes to any aspect of American life, and that includes our immigration laws."