Roger Federer and Rafael Nadal both voiced their displeasure at Andre Agassi after the former world number one revealed he took the recreational drug crystal meth in 1997 and lied about the reasons for a positive test.

"To me it seems terrible," world number two Nadal said at an awards ceremony in Madrid on Thursday.

"Why is he saying this now that he has retired?

"It's a way of damaging the sport that makes no sense.

"I believe our sport is clean and I am the first one that wants that.

"Cheaters must be punished and if Agassi was a cheater during his career he should have been punished."

World number one Roger Federer, who beat Agassi in the final of the 2005 US Open, also spoke of his sadness at the eight times major winner's admission in his new autobiography "Open".

"It was a shock when I heard the news," Federer said at a sponsors meeting at Kilchberg near Zurich.

"I am disappointed and I hope there are no more such cases in future.... our sport must stay clean."

However Agassi found support at home with fellow American and Wimbledon finalist Andy Roddick saying the 39-year-old remained his hero despite the revelations.

Roddick, the leading US men's player who lost to Federer in this year's Wimbledon final, was one of many compatriots who remained unfazed by Agassi's admissions.

"Andre is and always will be my idol. I will judge him on how he has treated me and how he has changed the world for (the) better," Roddick wrote on his Twitter page.

Roddick said Agassi's letter to the ATP, in which he told the governing body he had failed a drugs test because his drink had been spiked, came at a time when the player was far from his peak.

"To be fair, when Andre wrote the reported letter, he was well outside the top 100 and widely viewed as on the way out," said Roddick.

Women's world number two Serena Williams reacted to the news by plugging her own book.

"I don't even know what crystal meth is so, you know, that's what my reaction to it is. I haven't read anything about Andre Agassi's book. All I know is that I have a book coming out," she told reporters at the WTA Championships in Doha.

Serena's sister Venus, the world number seven, added: "His book will probably sell. It seems very interesting, to say the least."

US media has been restrained in its response to Agassi's admissions, which have appeared in excerpts from the book.

The New York Times noted Agassi was able to bounce back from his dark spell and enjoy a successful end to his career.

"The question is: Might it all have turned out differently without Agassi's reprieve from the doping panel, without his lie?" it asked referring to the five majors he won after 1997.

However, CBS columnist Ray Ratto questioned the motive behind Agassi's revelations.

"We're not here to kick a guy now that he's back up, although in fairness we've always found honesty to be more refreshing when it doesn't come at $31.99 a copy."