Some of the leading directors at this year's Cannes film festival have signed a petition urging Swiss authorities to reject a U.S. request to extradite Roman Polanski over a decades-old sex charge.

The petition, signed by France's Jean-Luc Godard, Mathieu Amalric and Xavier Beauvois among others, said that the United States' extradition request was "based upon a lie", a similar argument to that made in court recently by Polanski's lawyers.

The filmmakers are all part of the official selection at this year's Cannes film festival, which runs from May 12-23.

Polanski's lawyers argued that sealed testimony given by a prosecutor in the 1970s case would demonstrate that Los Angeles authorities gave inaccurate information in their request to extradite Polanski from Switzerland to California to face sentencing.

On Monday, a Los Angeles judge rejected a request to unseal testimony, saying that the Swiss authorities had all the information they needed to decide whether or not to extradite the 76-year-old Oscar winner.

The petition, on the website of French philosopher Bernard-Henri Levy, said: "They hereby appeal to the Swiss authorities, entreating them not to believe the word of Governor Schwarzenegger and the prosecutors of the state of California."

Levy added in a statement: "No matter how brilliant the films presented at this new festival, a man will shine in his blinding absence: Roman Polanski."

The French-Polish director is being detained at his home in Switzerland, where he was arrested on a U.S. warrant last year.

Los Angeles prosecutors want the "Chinatown" director to return to California to be sentenced for having illegal sex with a 13-year-old girl in 1977.

The filmmaker fled Los Angeles in 1978 believing the original judge in the case, who has since died, would renege on an agreement to limit his sentence to 42 days already served in an institution for psychiatric evaluation.