UPDATED 5:05 p.m. ET
(CBS News) -- President Obama says his position on same-sex marriage has evolved.
Three days after Vice President Joe Biden said he is "absolutely comfortable" with two men or two women getting married, Mr. Obama told ABC News in a hastily arranged interview that "same sex couples should be able to get married."
"I have to tell you that over the course of several years as I have talked to friends and family and neighbors when I think about members of my own staff who are in incredibly committed monogamous relationships, same-sex relationships, who are raising kids together, when I think about those soldiers or airmen or marines or sailors who are out there fighting on my behalf and yet feel constrained, even now that Don't Ask Don't Tell is gone, because they are not able to commit themselves in a marriage, 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," Mr. Obama said in an interview with Robin Roberts broadcast in a special report this afternoon. More from the interview will be broadcast tonight and tomorrow morning.
The president, who had previously said his position on the matter isis now the first sitting U.S. president to back the rights of same-sex couples to marry.
In 1996, as a candidate for the state Senate in Illinois, Obama offered "unequivocal" support for same-sex marriage but later changed his position.
As a candidate for president in 2008, Mr. Obama said he supports civil unions, but declined to back same-sex marriage.
When he signed the legislation repealing the Pentagon's 1993 law prohibiting openly gay members of the military, Mr. Obama was asked about his opposition to same-sex marriage and said his "feelings about this are constantly evolving."
"I struggle with this. I have friends, I have people who work for me who are in powerful, strong, long-lasting gay or lesbian unions. And they are extraordinary people. And this is something that means a lot to them and they care deeply about," he said about a year and a half ago.
Pressure again mounted on Mr. Obama to explain his position after Biden and Education Secretary Arne Duncan essentially backed same-sex marriage this week.
that "I am absolutely comfortable with the fact that men marrying men, women marrying women, and heterosexual men and women marrying another are entitled to the same exact rights, all the civil rights, all the civil liberties."
Duncan told MSNBC Monday he believes same-sex couples should be allowed to get married. Asked why he had never said so publicly before, he said "I don't know if I've ever been asked."
ABC News said Roberts asked if First Lady Michelle Obama had a role in his decision.
"This is something that, you know, we've talked about over the years and she, you know, she feels the same way, she feels the same way that I do. And that is that, in the end the values that I care most deeply about and she cares most deeply about is how we treat other people and, you know, I, you know, we are both practicing Christians and obviously this position may be considered to put us at odds with the views of others but, you know, when we think about our faith, the thing at root that we think about is, not only Christ sacrificing himself on our behalf, but it's also the Golden Rule, you know, treat others the way you would want to be treated. And I think that's what we try to impart to our kids and that's what motivates me as president and I figure the most consistent I can be in being true to those precepts, the better I'll be as a as a dad and a husband and, hopefully, the better I'll be as president," he said, according to ABC's website.
The issue complicates Mr. Obama's re-election efforts. Many conservative Democrats in key swing states like North Carolina and Ohio are opposed to same-sex marriage. Voters ininto their Constitution.
At the same time, the president has a multi-million dollar fundraiser this week with actor George Clooney and one with singer Ricky Martin next week. It's likely that many of the donors at those events back same-sex marriage.
Opponents to same-sex marriage accused him of pandering to campaign donors
"We think it's a huge mistake. President Obama is choosing the money over the voters the day after 61 percent of North Carolinians in a key swing state demonstrated they oppose gay marriage," said Maggie Gallagher, co-founder of the National Organization for Marriage and director of the Culture War Victory Fund.
Senior administration officials told reporters they were looking for the "right time" to make this announcement and conceded that Biden's remarks expedited the schedule, CBS News chief White House correspondent Norah O'Donnell reports.
"I have the same view on marriage that I had when I was governor and that I expressed many times. I believe marriage is a relationship between a man and a woman," Romney told reporters in Oklahoma after Mr. Obama's interview aired on ABC.
Public attitudes toward same-sex marriage have shifted in the past decade and a half. About 50 percent of Americans now support same-sex marriage, according to a Gallup poll released Tuesday. In 1996, the figure was just 27 percent.
New York Mayor Michael Bloomberg praised the decision as "a major turning point in the history of American civil rights."
"No American president has ever supported a major expansion of civil rights that has not ultimately been adopted by the American people - and I have no doubt that this will be no exception," Bloomberg said.