Washington, May 10 (IANS): President Barack Obama has become the first president in US history to come out in support of the same-sex marriage, injecting one of the most contentious issues into political debate ahead of the November poll.

Ending two years of "evolving" on the issue of gay marriage, Obama said in an interview with ABC News Wednesday, "At a certain point I've just concluded that 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."

The announcement put Obama squarely at odds with presumptive Republican presidential nominee Mitt Romney, who on Wednesday said during an appearance in Oklahoma, "I believe marriage is a relationship between a man and a woman."

Obama too once opposed gay marriages. He later indicated his views were "evolving."

"I had hesitated on gay marriage, in part, because I thought civil unions would be sufficient," Obama said.

"I was sensitive to the fact that -- for a lot of people -- that the word marriage is something that provokes very powerful traditions and religious beliefs."

But, Obama said, his thinking shifted as he witnessed committed same-sex marriages and thought about US service personnel who were "not able to commit themselves in a marriage."

With a Gallup Poll released Tuesday indicating that 50 percent of Americans believe same-sex marriages should be recognized by law as valid and 48 percent saying such marriages should not be legal, it was not clear how Obama's announcement might play out in the November poll, expected to be dominated by economic issues.

Obama, according to the White House, was "disappointed" by Tuesday's vote on the issue in North Carolina, which voted to implement a state constitutional ban on same-sex marriage, which was already prohibited by state law.

Supporters of the measure pushed for the constitutional amendment, arguing that it was needed to ward off future legal challenges.

Obama said Wednesday he supports the concept of states deciding the issue on their own, ABC News reported.

Before Tuesday, 30 states had voted in favor of constitutional amendments that seek to defend traditional definitions of marriage as a heterosexual union. Massachusetts, Connecticut, Iowa, Vermont, New Hampshire, New York and the District of Columbia issue marriage licenses to same-sex couples.