US President Barack Obama has said for the first time in an interview that same-sex couples should be able to get married.

"I've just concluded, for me, personally, it is important for me to go ahead and affirm that I think same-sex couples should be able to get married," Mr Obama said in an interview with ABC News.

However, he went on to say that it should be up to individual states to decide the issue.

Mr Obama said his position had evolved partly after talking to his two daughters, who had some friends who had same-sex parents.

"It wouldn't dawn on them that somehow their friends' parents would be treated differently. It doesn't make sense to them and frankly, that's the kind of thing that prompts a change in perspective," Mr Obama said in the interview.

The president came under increasing political pressure on gay marriage after Vice President Joe Biden said on NBC's Meet the Press on Sunday that he was "absolutely comfortable" with same-sex marriage.

US Education Secretary Arne Duncan said this week that he was also in favour of the concept.

Some political analysts have warned that Mr Obama could be entering a political minefield.

Yesterday, voters in North Carolina approved a state constitutional amendment forbidding gay marriages, civil unions and domestic partnerships.

The measure was passed by 61% to 39% after similar state constitutional amendments were approved in some 30 US states.

The amendment solidifies and expands already enacted North Carolina law forbidding same-sex marriage.

Mr Obama came to the position he elucidated through a long period of reflection and following pressure from his political base, which includes gay and lesbian groups.

In 2004, he said for religious reasons that he believed that "marriage is between a man and a woman," but added that he favoured a "bundle" of civil rights for gays and lesbians.

"What I believe in my faith ... a man and a woman when they get married are performing something before God."

In 2010, Mr Obama said "my feelings are constantly evolving" on gay marriage, and said he was in favour of civil unions for gays and lesbians that have strong civil protections.

In 2011, Mr Obama said he was "still working on it."