WASHINGTON: US Vice President Joe Biden has apologized to President Barack Obama in the Oval Office for remarks seen as forcing his boss into an early endorsement of same-sex marriage.

Biden said sorry for the furor on Wednesday before Obama became the first president to openly declare, in an interview with ABC News, that he favored gay marriage, sources familiar with the conversation said.

Officials earlier said Obama had already decided to back gay marriage before the Democratic National Convention in September, but that Biden's enthusiastic endorsement of it on a television show on Sunday forced him into an early move.

“The president has been the leader on this issue from day one and the Vice President never intended to distract from that,” Biden's spokeswoman Kendra Barkoff said.