Film director Roman Polanski could face two years in prison if extradited to the United States after fleeing sentencing in California on child sex charges in 1978, the Swiss justice ministry said.
"The United States want him to be extradited for sexual intercourse with a minor. This carries a maximum sentence of two years under U.S. law," justice ministry spokesman Folco Galli said on Friday.
The United States had formally asked Switzerland to extradite Polanski, the ministry said earlier, adding it would reach a decision based on a hearing and information provided by Polanski's lawyer, but that there was no deadline.
"If he agrees voluntarily to the extradition, the process can be concluded rapidly," Galli said. "If he fights it all the way, it will take months and months."
Polanski will be able to appeal against any extradition decision to the Swiss Federal Criminal Court and, in the last instance, the Federal Supreme Court, the ministry said.
The 76-year-old Oscar-winning director, who holds dual French and Polish citizenship, was arrested to comply with a U.S. warrant when he flew into Switzerland on September 26 to receive a lifetime achievement award at a film festival.
Polanski fled the United States when he was due to be sentenced for having unlawful sex with a girl aged 13.
U.S. judicial sources have said the extradition process is complex and could take years if Polanski challenges it.
A Swiss court this week rejected a bid by Polanski for release on bail, saying the risk that he would flee was too high.
Polanski's lawyer Herve Temime told Reuters that his client's strategy remained unchanged.
"Mr. Polanski will continue to fight this extradition request and demand that he be freed," he said.
Turbulent lifePolanski was originally indicted on six charges, including rape, for having sex after plying the girl with champagne and drugs. He pleaded guilty to a single count of having sex with a minor and spent 42 days in prison undergoing psychiatric tests.
But he fled the United States before the case was concluded because he believed a judge would sentence him to up to 50 years behind bars despite a plea agreement for time already served.
The Swiss ministry noted that Polanski had admitted to unlawful sex with a minor during the U.S. investigation: "He is wanted by the U.S. authorities with a view to passing sentence for this offence," it said.
U.S. law changed on July 1, 1977, reducing the maximum sentence Polanski could face for this offence to two years, the ministry said.
"Although Polanski committed the offence before this date, he was not due for sentencing until after July 1, 1977, meaning that sentencing according to the new law applies," said Galli.
Polanski has avoided countries such as Britain that have extradition treaties with the United States, but he repeatedly visited Switzerland, where he owns a chalet in the mountain resort of Gstaad, though he was only arrested on this occasion.
He has never returned to Los Angeles, where his pregnant wife, actress Sharon Tate, was murdered by followers of Charles Manson in 1969.
Polanski was born in Paris to Polish-Jewish parents in 1933. His mother died in the Nazi concentration camp at Auschwitz.
His first full-length feature, "Knife in the Water", won a number of awards, and his reputation grew with "Repulsion", his study of a woman terrified by sex who becomes a murderer.
Polanski, who is married to the French actress Emmanuelle Seigner and has two children with her, scored huge hits in the United States with his 1968 horror thriller "Rosemary's Baby" and his 1974 corruption thriller "Chinatown".
He won his first and only Best Director Oscar in 2002 for "The Pianist", the story of a Polish-Jewish musician who sees his world collapse with the outbreak of World War Two. (Additional reporting by Jason Rhodes in Zurich and Elizabeth Pineau in Paris; Editing by Kevin Liffey)