MADRID, Spain (AP) – Floyd Landis said the high testosterone levels that caused him to fail a drug test at the Tour de France are the result of his natural metabolism _ not doping of any kind _ and he will undergo tests to prove it.

“We will explain to the world why this is not a doping case but a natural occurrence,” Landis said Friday in his first public appearance since the doping test cast doubt on his title, one of the most stirring comeback wins in Tour history.

Landis said in a teleconference Thursday that he had no idea what may have tripped the test following the race’s 17th stage, where he made his heroic charge into the Alps last week.

But on Friday he was adamant that the reading is the result of his natural physiology.

“I would like to make absolutely clear that I am not in any doping process,” Landis said. “I ask not to be judged by anyone, much less sentenced by anyone.”

Landis is still awaiting results from a backup sample, which will clear him if it comes back negative. He said Friday that he would undergo additional testing to show that his body produces a high level of testosterone naturally.

If ultimately proven guilty, he could be stripped of the Tour title and fired from the team. Switzerland-based Phonak said it would ask that the backup sample be tested in the next few days.

The team suspended Landis after the International Cycling Union notified it Wednesday that he had an “unusual level of testosterone/epitestosterone” when his test was taken last Thursday, the day he staked his comeback in the Alps.

Landis said he was shocked when told of the initial positive result. He said he had been tested six other times during the tour, and many other times during the year.

His voice was subdued and at times downcast on the Thursday call, when he said he expected to clear his name but never to truly shake the disgrace of doping. But Landis turned defiant in his Friday appearance, chastising the media for implying that he was accused of doping and defending himself as an honest competitor who devoted his life to his sport.

“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. “I was the strongest guy. I deserved to win, and I’m proud of it.”