Tennis has removed the opportunity for players to cheat with drugs, Andre Agassi said on Thursday.

Despite a rash of positive tests for nandrolone which have brought the sport's anti-doping policy into doubt, the eight times Grand Slam champion said testing was so extensive now that cheats could not get through.

He added, however, that contamination of supplements could remain a problem.

"With our system, we test so often, so extensively, that we have absolutely removed the possibility of someone taking performance enhancing drugs for cheating," said Agassi during the Nasdaq-100 tournament.

Eight players have tested positive for the steroid nandrolone since August 2002, the most high profile of whom was Britain's Greg Rusedski.

Rusedski and the other seven players were all exonerated by a tribunal after the players' organisation ATP said the nandrolone might have come from contaminated supplements handed out by its own trainers.

Dozens more players tested since August 2002 have shown higher than usual levels of the steroid in their system, though not enough to register a positive test.

The ATP has since said that there was no proof that its trainers were the source of the contamination, leaving testing authorities none the wiser as the how the nandrolone got into players' systems.

"While there are drugs out there that have been abused I don't think in tennis we've seen it...as a form of cheating," Agassi said.

Agassi, who attended the first meeting of the ATP's specially convened taskforce on supplements on Tuesday, said he had complete faith that tennis was clean.

He said he and his fellow players were frustrated that the nandrolone problem was bringing tennis into disrepute.

"Our sport goes to such lengths to avoid the possibility of drug cheating. To go to those lengths and then have the situation we have and for our sport to be defaced on the covers of magazines and newspapers is really frustrating," he said.

Since the Rusedski case, players have been advised not to take any kind of supplement or electrolyte replacement product for fear of contamination. Agassi said this put extra pressure on players.

"Our product suffers if we don't give our bodies what they basically need," he said. "And I don't think it's good for tennis to see great players cramping out there on the court. It's a great sport and great product and if you deny the players essential vitamins and supplements...then you are tearing at the heart of the product.

"I can consider it lucky that anything I have taken hasn't manifested itself in cross contamination," Agassi added..