Vice President Joe Biden has officiated a gay wedding, a first for the early proponent of same-sex marriage.

Biden presided over the union of Joe Mahshie and Brian Mosteller, both longtime White House aides. The White House says the couple asked Biden to officiate.

Biden has never officiated a wedding before, so he got a special temporary certification from the District of Columbia to make it legal.

The afternoon ceremony took place Monday at the Naval Observatory, the vice president's official residence, with immediate family attending.

Biden publicly backed gay marriage in 2012 in the run-up to President Barack Obama's re-election. The announcement put pressure on Obama to declare his own support shortly after.