Polanski, 76, was arrested in Switzerland during the weekend after U.S. authorities asked Swiss police to execute a warrant in the Oscar winner's decades-old rape case.
The famous film director, who was born in and lives in France, has not traveled to the United States since he pleaded guilty in a Los Angeles court to having unlawful sex with a minor in 1977 and then fled the country before he could be sentenced. He was accused of drugging and raping a 13-year-old girl.
The Hollywood Reporter quoted attorney Herve Temime as saying the first step is to try to convince Swiss authorities to release Polanski.
"After that, his defense team will demonstrate the illegal nature of the extradition request he is facing," Temime said in a statement.
"He is in a fighting mood and determined to defend himself," Temime separately told France Info radio.