Source: Obama had planned to announce support for same-sex marriage next week
Senior administration officials say Vice President Biden's comments on NBC's "Meet the Press" sped up the timeline and forced the president's hand.
"I had already made a decision that we were going to probably take this position before the election and before the convention," he told ABC News.
Mr. Obama added that Biden did jump the gun, but he is not upset about it.
"[Biden] probably got out a little bit over his skis but out of generosity of spirit," Mr. Obama said. "Would I have preferred to have done this in my own way, in my own terms, without I think there being a lot of notice to anybody? Sure. But all's well that ends well."