New York, USA - Hanks had come under attack from the Church of Latter Day Saints after he criticised Mormons who backed Proposition 8, a constitutional amendment to the state's law.
Speaking last week at the premiere in Los Angeles of Big Love, a television series which he produces about a polygamist Mormon sect, Hanks had said that the proposal amounted to "codified discrimination".
He added: "There are a lot of people who feel that is un-American and I one of them." Following the outcry from church members, the star of Forrest Gump has backtracked.
"I believe Proposition 8 is counter to the promise of our Constitution; it is codified discrimination," he said in a statement through his publicist.
"But everyone has a right to vote their conscience - nothing could be more American." He conceded his earlier remark "creates more division when the time calls for respectful disagreement".
He added: "No one should use 'un-American' lightly or in haste. I did. I should not have."