Paris (AFP) - Andre Agassi revealed on Friday he is happy to work unpaid as Novak Djokovic's coach and said he would be open to extending his relationship with the Serb at Wimbledon next month.

Eight-time Grand Slam champion Agassi teamed up with Djokovic ahead of the French Open, where the Serb is attempting to defend his title.

Agassi, who won Roland Garros in 1999, said he is not being paid to mentor Djokovic but simply wants to help him find his best form again.

"For me, I do this on my own time and my own dime," said Agassi.

"I don’t want money, I want to help him. And it helps the game. Him at his best is good for the game and it’s a way I can contribute."

Agassi initially committed to just a "few matches" with the former world number one, but the American told Eurosport he was open to working with Djokovic at Wimbledon.

"If he wants me there, yeah, I will come," said 1992 Wimbledon champion Agassi, speaking to Djokovic's former coach Boris Becker.

"It’s a lot of responsibility so whatever’s practical and achievable -– 100 percent I will make the effort."

Becker gave up coaching Djokovic last December after three successful years together, while the 12-time major winner split with long-time coach Marian Vajda last month.

He then named Agassi after he lost to Alexander Zverev in the Rome Masters final a fortnight ago.

Djokovic, speaking after needing five sets to see off Argentina's Diego Schwartzman 5-7, 6-3, 3-6, 6-1, 6-1 on Friday, confirmed that Agassi wasn't taking a fee.

"Everything that he said is completely true, so it's completely his decision," said the Serb.

"In terms of some plans for the future, we don't have anything set in stone. We don't say he's going to be here until this time or that time.

"You know, he's going to try his best to be in the biggest tournaments with me and as much as his family time allows and all the commitments that he has.

"We both agree that I'm going to need someone also day to-day basis that can work with him, but he's the man."

Agassi's other professional commitments at Roland Garros meant he only arrived for Friday's match midway through the second set.

"I don't have any expectations. I'm just trying to enjoy every possible moment that I have next to him

"As far as I'm concerned, I hope that that's gonna stay for a long time that we can create something that is going to go long term."