PARIS (AFP) - Real Madrid striker Karim Benzema admitted to investigators he was supposed to act as an intermediary between a friend and his French international teammate Mathieu Valbuena in a sex tape blackmail case, sources told AFP on Friday.

Benzema also told police he felt "stupid" when confronted with the evidence, said one source close to a case that has cast a shadow over the national team as France prepares to host Euro 2016 next year.

The centre-forward has been charged over the case in which Valbuena went to the police after being approached for money by men claiming to be in possession of a sex tape featuring the Lyon midfielder.

Benzema had initially denied any involvement following his arrest on Nov 5, but in a third session of questioning he began to open up.

He eventually admitted he was only trying to help Karim Zenati, a childhood friend from Lyon where the player grew up, who already had a criminal record.

"I feel embarrassed towards my friend Karim Zenati because when he came out of prison and even when he was inside, I looked after him. We're very close," Benzema said, according to the sources.

He added: "I was supposed to act as the go-between and develop a relationship between Mathieu (Valbuena) and Karim Zenati."

Police then produced the recording of a conversation between Benzema and Zenati, in which the footballer related - using a mocking tone - his conversation with Valbuena at the French national training base in Clairefontaine on Oct 5.

After hearing the tape, Benzema admitted: "I did have a conversation with Zenati, about how to bring up the subject with Mathieu Valbuena.

"It was not my aim that Karim Zenati benefited from this, I didn't think about that. I'm shocked. Honestly, I look stupid when I see all that," he said.

But he was not prepared to abandon his friend.

"Zenati is a serious person and someone I have confidence in," Benzema told police, the sources said.

Benzema's lawyer Alain Jakubowicz told AFP the conversation with police showed that his client "had no malicious intent".

Neither Benzema nor Valbuena were selected for the squad for France's friendly against Germany on Friday, nor for the game against England on Tuesday.

Real Madrid president Florentino Perez has pledged his "full support" for Benzema.