The recent endorsement of gay marriage by U.S. President Barack Obama was a milestone for the lesbian, gay, bisexual and transgender community and could gain more support among younger voters who already overwhelmingly back same-sex marriages, according to a prominent American gay rights activist.

Mark Bromley, chairman of the Council for Global Equality, a 21-group coalition seeking a clearer and stronger U.S. position on global LGBT issues, said Monday in Tokyo that while same-sex marriage would be an issue in the U.S. presidential campaign, it would not take center stage in a way that it could hurt the re-election chances of Obama, who in May became the first sitting U.S. leader to support gay marriage.

"I am optimistic that the polling is going to show eventually that it's going to have a minimum impact on actual votes, and eventually gain some ground," Bromley said during a news conference at the U.S. Embassy in Tokyo.