WASHINGTON - THE White House on Monday registered disapproval after a comedian at a gala dinner featuring President Barack Obama likened a top conservative radio host to a Sept 11 hijacker.

Sharp-tongued comedian Wanda Sykes brought the house down at the annual dinner of the White House Correspondents' Association on Saturday night, but some commentators thought she went too far in talking about Rush Limbaugh.

White House spokesman Robert Gibbs, who was also on the top table at the dinner with Mr Obama, said he had not talked to Mr Obama specifically about the joke.

But he added: 'I think there are a lot of topics that are better left for serious reflection rather than comedy.'

'I think there's no doubt that 9/11 is part of that,' Mr Gibbs said, pointing out the fact that Sykes was booked by the association not the White House.

At the annual dinner, where Washington political types mix with A-list Hollywood stars, Sykes referred to Limbaugh, a fierce Obama critic, as the '20th hijacker,' accused him of treason and referenced his former addiction to pain killers.

Riffing off Limbaugh's controversial recent remark that he hoped Mr Obama fails, Sykes said 'I hope his kidneys fail, how about that?'

Mr Obama, seated close to Sykes on the stage, was seen to smile uncomfortably at the remark and reach for a glass of water as the comedian asked 'too much?' -- AFP