Roman Polanski's legal team fired the first shot Tuesday in a lengthy battle over his possible extradition to the United States, asking a Swiss court to release the famous filmmaker from prison immediately.

The Swiss Federal Criminal Court announced the filing and said a decision would be made "within the next weeks," but experts said a swift release was unlikely, and it appeared that the 76-year-old director could remain in jail for at least a few months.

Even if the court rules in Polanski's favor, the decision would probably be appealed immediately by the Swiss government, extending his incarceration in a Zurich cell.

Meanwhile in Poland, the prime minister urged restraint after two days of heated calls from government officials for Polanski's release. French leaders who had also been outspoken in support of the filmmaker said their consul had visited him in detention.

Authorities in Los Angeles consider Polanski a convicted felon and a fugitive, and Switzerland says there has been an international arrest warrant out on him since 2005.

Polanski was accused of plying a 13-year-old girl with champagne and Quaaludes during a modeling shoot in 1977 and raping her. He was initially indicted on six felony counts, including rape by use of drugs, child molesting and sodomy.

Facing life in prison if convicted, he agreed to plead guilty to the lesser charge of unlawful sexual intercourse.

In exchange, the judge agreed to drop the remaining charges and commute his sentence to the 42 days already served. But Polanski fled the country Feb. 1, 1978, the day he was scheduled to be sentenced, after learning that the judge told lawyers he planned to tack on more prison time.