In his drive to end a ban on gays in the military, US President Barack Obama got an unexpected boost during his latest visit to Afghanistan, as a female singer performed 'I Kissed a Girl.' It was an unusual musical choice for a presidential event, but pop star Katy Perry's same-sex themed lyrics were in tune with the political debate back in Washington, where senators were arguing over the merits of opening up the armed forces to openly gay troops. As a throng of US troops waited for Obama to take the stage in his unannounced visit to Bagram Air Base Friday, a band warmed up the crowd with Perry's breakthrough single. 'I kissed a girl and I liked it,' goes the 2008 hit, 'It felt so wrong, It felt so right.' Obama has called on Congress to repeal the current law, known as 'Don't Ask, Don't Tell,' which obliges soldiers to hide their sexual orientation or else face expulsion from the military. Another pop star, Lady Gaga, has already entered the political fray on the issue, attending rallies and issuing videos urging an end to the ban, saying it unfairly bars homosexuals from serving their country in uniform. 