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Embattled Tour de France winner Floyd Landis proclaimed his innocence Friday, one day after his team informed international cycling officials that he had tested positive for abnormally high levels of testosterone.

At a press conference in Madrid, Landis asked that he not be judged prematurely and said he was not "in any doping process.

"I declare convincingly and categorically that my winning the Tour de France has been exclusively due to many years of training and my complete devotion to cycling," he said.

Landis claims the high levels of testosterone detected in the test were a result of his natural metabolism, not due to doping. The rider volunteered to undergo additional tests to clear his name.

"We will explain to the world why this is not a doping case but a natural occurrence," he said. "All I'm asking for is that I be given a chance to prove I'm innocent."

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It was the American cyclist's first public appearance since a positive doping test cast doubt on one of the most stirring Tour de France comeback wins in history, and the first since his team, Phonak, announced Thursday that that he tested positive for abnormal levels of testosterone after the 17th stage of the Tour.

Landis defended himself as an honest athlete who has devoted his life to the sport.

"I was the strongest guy. I deserved to win, and I'm proud of it," he said, adding that he hoped the additional testing would be completed as soon as possible.

The rider attended the press conference with his lawyers, who said Landis would be heading back to the United States Friday but did not indicate exactly where in the country he would be going.

Landis had an exemption from the Tour to take cortisone shots for pain in his hip, which will require surgery for a degenerative condition, and was taking an oral medication for hyperthyroidism. He and his doctor were consulting with experts to see if those drugs might have thrown off his testosterone levels.

News of Landis' positive test shocked the cycling world, which has been under a cloud following a wide-ranging doping investigation in Spain that led to the barring of several of the world's leading cyclists from the tournament.

Jean-Francois Lamour, France's Minister for Youth, Sports and Associations, said the scandal was a "serious blow" to the Tour de France's credibility.

"The whole (cycling) culture must change," he said. "I don't understand why some spend more time trying to cheat than preparing for the race."

Landis's lawyer, Luis Sanz, said he fully expected the backup test to come back with the same result, since the elevated testosterone was produced naturally by Landis's body, and said further tests must be conducted to prove his client's innocence.

"The result of the counter-analysis is, with absolute and total certainty, going to be the same as that already communicated by the laboratory," Sanz said.

On the eve of the Tour's start, nine riders — including pre-race favorites Jan Ullrich and Ivan Basso — were ousted, implicated in a Spanish doping investigation.

The names of Ullrich and Basso turned up on a list of 56 cyclists who allegedly had contact with Spanish doctor Eufemiano Fuentes, who's at the center of the Spanish doping probe. Landis was not implicated in that investigation.

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