New Yorkers celebrate approval of Gay marriage in New York

The party's platform drafting committee voted to include language backing gay marriage during a weekend meeting in Minneapolis, the official said. Democratic delegates will formally approve the platform during the party convention in Charlotte, N.C. in early September.

President Barack Obama will officially accept his party's nomination at the convention, which marks the start of the fall campaign blitz. Republican rival Mitt Romney will get the GOP nomination a week earlier during his party's convention in Tampa, Fla.

Seeking to ramp up enthusiasm among Democrats, party officials said Sunday that former President Bill Clinton will deliver the nominating speech on Wednesday night of the convention. Obama and Biden are to speak on Thursday, the convention's final night.

Several prominent Democrats began pushing earlier this year for support of same-sex marriage to be included in the convention platform, which lists principles the party supports. The effort got a boost in May when Obama voiced his personal support for same-sex unions.

The Democratic official would not comment on the exact language of the pro-gay marriage plank approved by the drafting committee. It was unclear if the party would call for any national action to legalize gay marriage.

Obama has said he considers gay marriage to be a state issue, not a federal matter.

The official spoke on the condition of anonymity because they were not authorized to speak publically about the platform committee's decision.

The move was first reported by The Washington Blade.