Speaking during a recording of the ABC program "The View" for broadcast Tuesday, Obama said he believes same-sex couples should have the right to marry but added "this is something that historically has been determined at the state level."
When pressed, Obama declined to say he would push for the repeal of DOMA, the Clinton-era law defining marriage as the legal union of one man and one woman, saying, "Congress is clearly on notice that I think it's a bad idea."
Obama nonetheless said there is a clear distinction between himself and former Massachusetts Gov. Mitt Romney, the likely Republican presidential nominee.
"This is going to be a big contrast in the campaign because you've got Governor Romney saying we should actually have a constitutional amendment installing the notion that you can't have same-sex marriages," Obama added.
"We don't think the Defense of Marriage Act is constitutional," he said.
Obama publicly declared his support for same-sex marriage last week in an exclusive interview with ABC News after opposing marriage equality for years.