France's Gasquet is ranked 23rd in the world rankings
France's Richard Gasquet has been provisionally suspended after testing positive for cocaine.
The 22-year-old, who could face a two-year ban from the sport, failed the test at the Miami Masters in March.
"His provisional suspension begins today (Monday)," said Dr Stuart Miller, the head of the International Tennis Federation's anti-doping commission.
Gasquet said: "I want to prove my innocence and will explain myself at an appropriate time."
Gasquet, who reached the last four at Wimbledon in 2007 and has a career-high ranking of seventh, said he had submitted himself to an independent test and that a hair analysis "showed no trace of cocaine".
But traces of the drug were found in his urine sample.
He said: "The test of the B sample submitted at the end of March 2009, confirmed the positive result of the A sample taken on the same day.
"Given the complexity of the case, I am gathering the evidence of my innocence and will later set a date to make further comments."
ITF spokesman Neil Robinson said an anti-doping tribunal should be assembled within 60 days to hear the case.
"He's suspended until the end of the hearing," said Robinson.
"The ideal timeframe is within 60 days, but people have to fly in from all over the world for the tribunal."
In a statement released on Sunday, the French Tennis Federation said it was "very surprised" by the news.
"If confirmed according to official proceedings, it would be very sad for Richard Gasquet, for tennis in general and for French tennis in particular, whose image would be tarnished," read the FFT statement.
The FFT will follow with great attention the developments of this case, avoiding making hasty judgements and is anxious to leave the player to organise his defence for the international tennis bodie
"At this stage, the FFT does not wish to make further comments because it is down to the anti-doping authorities, within the International Tennis Federation (ITF), to assess such a case and it is not for the FFT to intervene.
"The FFT will follow with great attention the developments of this case, avoiding making hasty judgements and is anxious to leave the player to organise his defence for the international tennis bodies.
"If the facts are correct, however, this would be particularly unfortunate in light of all the efforts of the FFT in terms of deterring athletes [from using banned substances]."
Gasquet has been regarded as the brightest young talent in French tennis since turning professional in 2002.
He ended his debut season as the youngest player to finish in the top 200 in the world rankings, and was also the youngest to qualify for an ATP Masters at Monte Carlo.
Gasquet has won five singles titles and more than US$4m (£2.7m) in prize money during his career.