WASHINGTON ? The United States said Monday it was "disappointed" by a Swiss decision to free Roman Polanski and vowed to keep seeking "justice" against the director wanted on underage sex charges.

"We are disappointed by it," State Department spokesman Philip Crowley told reporters.

"The rape of a 13-year-old girl by an adult who should know better and does know better is a crime," he said. "We will continue to seek justice in this case and we will evaluate our options."

The Oscar-winning French-Polish director has been a fugitive from US justice for decades since he fled before sentencing after pleading guilty to having sex with a 13-year-old after plying her with drugs and champagne in 1977.

"We have not forgotten about this case," Crowley said. "We think it sends a very important message regarding how women and girls are treated around the world."

The Swiss government said it would not extradite him due to a "fault" in the US extradition request relating to whether Polanski had already served his sentence in the United States and said it could not appeal the decision.

"Please," Crowley said dismissively of the Swiss rationale. "A 13-year-girl was drugged and raped by an adult. This is not a matter of technicality."

In Los Angeles, County District Attorney Steve Cooley denied the extradition request was at fault.

"Our office complied fully with all of the factual and legal requirements of the extradition treaty and requests by the US and Swiss Departments of Justice and State," Cooley said in a statement.

"We will discuss with the Department of Justice the extradition of Roman Polanski if he's arrested in a cooperative jurisdiction" he added.

Switzerland's decision not to extradite Polanski, said Cooley, "is a disservice to justice and other victims as a whole."