Lance Armstrong has confirmed that he has given up his fight against drug charges from the US anti-doping agency.

The American cyclist was disputing claims that he had used performance-enhancing drugs since 1996, but he will not carry on the fight ahead of a Friday deadline.

"I know who won those seven Tours," Armstrong said in a statement. "The toughest event in the world where the strongest man wins. Nobody can ever change that."

Despite the 40-year-old's insistence that he is innocent, his refusal to fight his case could result in a lifetime ban from cycling as well as possibly being stripped of his seven Tour de France titles.

Armstrong has indicated that he will continue his charity work and spend time with his family instead of continuing the dispute with the anti-doping agency.