LONDON (AP):

The World Anti-Doping Agency has asked tennis to investigate André Agassi's admis-sion that he took crystal meth in 1997.

WADA Director General David Howman would not elaborate on what he wrote in the letter sent to the ATP, but he told The Associated Press he hoped it "would bring a considered response".

"Our task is to protect the clean athletes and to make sure that these sorts of things don't recur," Howman said, by telephone. "And, if we didn't take any steps, somebody would be knocking on our door saying, 'Well, what are you doing about this?'"

Agassi wrote in his soon-to-be-released autobiography, Open, that he ingested crystal meth and then lied to the governing body of men's tennis to avoid a suspension after failing a doping test.

Howman said the letter was specifically addressed to the ATP, but the International Tennis Federation would be made aware of it.

"The ATP can confirm it has received a letter from WADA," the tour said in a statement emailed to the AP, on Monday. "When it responds, it will do so directly to WADA and not through the media."

The statement continued, in part: "The ATP would also like to reiterate its policy of not commenting on anti-doping test results unless and until an anti-doping violation has been found."

That was the crux of what the ATP said last week, when excerpts from the book revealed that eight-time Grand Slam champion Agassi admitted he used crystal meth in 1997 and said he had wriggled his way out of a suspension after a positive drug test that year. Other tennis and doping authorities initially expressed disappointment at those revelations, but they also said it was too late for sanctions because of an eight-year limitation rule.