Lance Armstrong has decided he will no longer contest charges by the U.S. Anti-Doping Agency that he used performance-enhancing drugs during his career.

"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 Thursday night in a statement.

Armstrong added, "If I thought for one moment that by participating in USADA's process, I could confront these allegations in a fair setting and -- once and for all -- put these charges to rest, I would jump at the chance."

Calling the process "one-sided and unfair," Armstrong still maintained his innocence.

"Regardless of what Travis Tygart says, there is zero physical evidence to support his outlandish and heinous claims," he said Thursday.

The USADA on Thursday said it has not received direct confirmation from Armstrong that the retired cyclist will cease his fight against the doping charges.  However, the agency's CEO, Travis Tygart, responded to Armstrong's announcement.

"It is a sad day for all of us who love sport and our athletic heroes.  This is a heartbreaking example of how the win-at-all-costs culture of sport, if left unchecked, will overtake fair, safe and honest competition, but for clean athletes, it is a reassuring reminder that there is hope for future generations to compete on a level playing field without the use of performance-enhancing drugs," Tygart said in a statement Thursday.

Tygart says the agency will strip Armstrong of his seven Tour de France titles and ban him from professional cycling for life.