Bradley Cooper has been branded a ''diva''.

The actor and his co-stars were reportedly three hours late to 'The Hangover Part III' premiere in Rio de Janeiro earlier this week, and when he finally rocked up, Bradley seemed sullen and gave monosyllabic answers on the red carpet.

Bradley, 38, reportedly ignored fans waiting to meet him and stayed silent when questions were posed to him and his co-stars, only reluctantly speaking up when questions was exclusively for him.

When quizzed by a reporter what he would do if he had a hangover in Brazil, he snapped: ''I don't even drink anymore.''

Another asked, ''You were voted the sexiest man in the world...'', to which he quipped, ''It doesn't change anything for real. It's just something the media creates.''

Bradley's flirtatious relationship with his 'Silver Linings Playbook' co-star Jennifer Lawrence was also referred to, with a journalist teasing, ''Jennifer said you're a 'wet kisser'...''

Bradley sighed: ''We were joking.''

Meanwhile, rumours are also circulating that the comedy triolgy's 'Wolf Pack' gang - Bradley, Ed Helms and Zach Galifinakis - are not as friendly in real life.

Website Glamurama said: ''The gossip behind the scenes is that there was a disagreement between the team on Tuesday night at the hotel.''

However, Ed was on form during the promotional tour of Brazil, and burst into laughter when an interview he was giving at Fasano's Hotel in Rio was interrupted two monkeys jumped down from a nearby building, prompting co-star Heather Graham to stop and take a photo.