By Ian Youngs
BBC News Online entertainment staff in Cannes
The White House tried to halt the making and release of Michael Moore's new film Fahrenheit 9/11, the film-maker alleged in Cannes on Sunday.
Moore film is to get its world premier in Cannes
The director told a Cannes audience the Bush administration wanted to keep the film off screens in the run-up to November's US election.
The film examines the Iraq war and alleges connections between the Bush and Bin Laden families.
Fahrenheit 9/11 is to get its world premiere in Cannes on Monday.
Film studio Disney had backed out of a deal to distribute the film in the US for political reasons, Moore says.
He has given no evidence to substantiate his allegations, but said "someone connected to the White House" and a "top Republican" had put pressure on film companies not to release the film.
Moore said the few who had seen the film had told him
"the potential for this film to have an impact on the
election was much larger than they thought".
Undercover in Iraq
The film was originally scheduled to be released through Disney-backed independent studio Miramax, before Disney blocked it.
It is now expected to be released through a third party.
Disney accused Moore of engineering a dispute about the film's release to gain maximum publicity. It said it had blocked the film because it wanted to be impartial during the election, but strongly denied coming under any outside pressure.
The director has already shown the film at test screenings in the Midwest of the US.
"The reaction was overwhelming," he said. "People who were on the fence - undecided voters - suddenly weren't on the fence."
No-one from the White House was available to comment on his remarks.
Moore has also revealed that he had three undercover film crews embedded with US troops in Iraq.
"I was able to sneak three different freelance crews into Iraq," he said on Saturday.
The soldiers had "expressed disillusionment that they had been lied to", said Moore.
The film from Iraq was a "very important" part of the documentary, he added.
"It is certainly something the Bush administration does not want people to see," said Moore.