The French government has dropped its public support for Roman Polanski, saying the 76-year-old director "is neither above nor beneath the law".
The move follows a backlash against a campaign for Polanski's release, with several leading European politicians and cultural figures refusing to join.
He is being held in Switzerland on a US arrest warrant over charges of unlawful sex with a 13-year-old girl.
On Monday, the French foreign minister called for Polanski to be freed.
Polanski, who has dual French and Polish citizenship, was arrested on Saturday when he flew into the country.
He had been due to pick up a lifetime achievement prize at the Zurich film festival.
Speaking to reporters, French government spokesman Luc Chatel said: "We have a judicial procedure under way, for a serious affair, the rape of a minor, on which the American and Swiss legal systems are doing their job."
Polish Foreign Minister Radoslaw Sikorski and his French counterpart Bernard Kouchner have written to US Secretary of State Hilary Clinton calling for Polanski to be freed.
But the Polish Prime Minister Donald Tusk has distanced himself from the move by asking his ministers to show "greater restraint" in defending him.
Martin Scorsese is supporting his fellow director
He added that despite a "leading Polish director" being involved, it is still a "case of rape and of punishment for having sex with a child".
A member of the British parliament has called on the Council of Europe, of which he is also a member, to support Polanski's extradition to the US.
Denis MacShane said the film-maker "should be held accountable" for his actions.
French film-maker Luc Besson, who directed the 1994 movie Leon, has also refused to lend his support.
Speaking to French radio station RTL, he said: "I have a lot of affection for him, he is a man that I like very much ... but nobody should be above the law.
"I don't know the details of this case, but I think that when you don't show up for trial, you are taking a risk."
Despite that, Mr Polanski has no shortage of supporters, including at least 110 film industry figures who have signed a petition calling for his release.
Among them are Martin Scorsese, Woody Allen and David Lynch, as well as Wim Wenders, Pedro Almodovar, Tilda Swinton and Monica Bellucci.
Actor Peter Fonda said he thought "celebrating the arrest of Osama bin Laden and not the arrest of Polanski" was far more important.
Mr Polanski fled the US in 1978 before he was sentenced on a charge of unlawful sexual intercourse with a 13-year-old girl.
He has never returned and even missed receiving an Oscar for his 2003 film The Pianist.