GENEVA: The United States has formally asked Switzerland to extradite detained Oscar-winning director Roman Polanski over a three-decades-old child sex case, Swiss authorities said Friday.

"The US Embassy in Bern submitted the formal extradition request to the Federal Office of Justice on 22 October 2009, within the deadline of 40 days stipulated under the bilateral extradition treaty," the Swiss Federal Office of Justice said in a statement.

The request will now be forwarded to the canton of Zurich, where Polanski was detained upon his arrival on September 26 to collect an award at the city's film festival.

A local court will then hold a hearing and, "based on the results of the hearing and the information provided by Polanski's lawyer," the justice office will decide whether to accept the extradition request.

If it is accepted, Polanski can appeal against the justice office's decision before the country's top criminal court. He will also have a further chance to appeal to the federal supreme court, said the justice office.

Polanski's lawyer Herve Temime said the film director will fight the US request.

"Mr Polanski is not changing course. He will not accept the US extradition request," Temime told AFP without elaborating.

Polanski has been regarded as a fugitive by US authorities since he fled the United States in 1978 after admitting to sex with a 13-year-old girl.

He has asked to be released on bail pending extradition, but Switzerland's top criminal court on Tuesday rejected the request, saying there was a "high" risk that he could flee the country.