One Direction stars Niall Horan and Liam Payne will celebrate their 21st birthdays with a wild night out in the U.S.

Horan reaches the milestone in September (14), just two weeks after Payne, and the pair plans to mark the occasion with a drinking session on tour in America, where the legal age limit for alcohol consumption is 21.

Horan tells Irish radio station Spin 103.8, "I reckon myself and Liam are probably going to end up having a joint 21st because his birthday is about two weeks before mine... We'll have a few drinks there. We've been touring America for the past three years and not been able to touch a drop."

However, their bandmate Harry Styles will not be legally allowed to join in the booze-fuelled revelry - he does not turn 21 until next year (15).