AFP - French pop idol Johnny Hallyday leapt to the defence of detained Oscar-winning film maker Roman Polanski in a newspaper interview on Wednesday, saying he should be left alone.

Polanski, a fugitive in the United States, is in a Swiss jail pending legal wrangling over the US extradition warrant that led to his arrest in Zurich last month for a 1977 child sex case in California.

"Thirty-two years later, while the victim is asking for the case to be dismissed and after that man has changed his life, I feel that the way it has played out isn't very fair," Hallyday told the Swiss newspaper Le Matin.

"It's a trap. He was 44, he's now 76. Just leave the guy alone," said Hallyday.

The 66-year-old pop star who, like Polanski, owns a property in the Swiss Alpine resort of Gstaad, a playground for showbusiness stars in later life, said he could not judge the French-Polish filmmaker's acts.

"In that era Polanski's wife, Sharon Tate, was massacred, her baby was snatched from her belly. That was a horrible tragedy that could have perturbed him too," Hallyday told the newspaper.

In the same interview, Hallyday revealed that he would undergo an operation for a slipped disc on November 25, before taking a year off the concert scene.

He said he first suffered the injury during shooting for Hong Kong film maker Johnny To's 2009 thriller "Vengeance".