The USADA has officially stripped cyclist Lance Armstrong of his seven Tour de France titles after he dropped his fight against drug charges that threatened his legacy as one of the greatest cyclist of all time.

Armstrong, who retired last year, declined to enter USADA's arbitration process -- his last option -- because he said he was weary of fighting accusations that have dogged him for years. He consistently has pointed to the hundreds of drug tests that he has passed as proof of his innocence during his extraordinary run of Tour titles from 1999 to 2005.

"There comes a point in every man's life when he has to say, 'Enough is enough.' For me, that time is now," Armstrong said in a statement sent to The Associated Press. He called the USADA investigation an "unconstitutional witch hunt."

"I have been dealing with claims that I cheated and had an unfair advantage in winning my seven Tours since 1999," he said. "The toll this has taken on my family and my work for our foundation and on me leads me to where I am today -- finished with this nonsense."

USADA reacted quickly and treated Armstrong's decision as an admission of guilt, hanging the label of drug cheat on an athlete who was a hero to thousands for overcoming life-threatening testicular cancer and for his foundation's support for cancer research.

Armstrong disputed USADA's jurisdiction to strip the titles. He insisted that his decision is not an admission of drug use, but a refusal to enter an arbitration process he believes is unfair.

USADA also said it had issued Armstrong a lifetime ban on Friday. Under the World Anti-Doping Code, he could lose the bronze medal from the 2000 Olympics as well as any awards, event titles and cash earnings.

World Anti-Doping Agency president John Fahey said Armstrong must now live with the consequences of his decision not to continue fighting allegations against him.

"He had a right to contest the charges. He chose not to," Fahey said. "The simple fact is that his refusal to examine the evidence means the charges had substance in them. Under the rules, penalties can now be imposed."