Armstrong, who won the Tour de France an unprecedented seven straight times, said Thursday that he would not keep fighting the charges levied against him by the United States Anti-Doping Agency, which contended that he doped and was one of the ringleaders of systematic doping on his Tour-winning teams.
Armstong, who never tested positive during his career, has denied using performance enhancing drugs. He won the sport's ultimate contest from 1999 through 2005 and retired last year.
"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 released on his website. "I have been dealing with claims that I cheated and had an unfair advantage in winning my seven Tours since 1999. 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."
Armstrong, a survivor of testicular cancer and major fundraiser for research through his Livestrong foundation, had until Thursday night to inform USADA if he would fight the charges, with his last option being arbitration. The cycling champion refused, saying USADA was ''on a witch hunt" and didn't have the authority to impose a lifetime ban.
If the agency does impose a lifetime ban and recommend Armstrong be stripped of his titles, the International Cycling Union would have the final say.
Armstrong said his decision is not an admission of guilt.
"USADA cannot assert control of a professional international sport and attempt to strip my seven Tour de France titles," he said. "I know who won those seven Tours, my teammates know who won those seven Tours, and everyone I competed against knows who won those seven Tours."