Lance Armstrong has made a public appeal to the US Anti-Doping Agency to answer his correspondence to them.

The USADA confirmed this week that it had sent Armstrong written notification regarding "allegations of anti-doping rule violations" during his time with the United States Postal Service (USPS) cycling team.

The now-retired 40-year-old won seven Tour de France titles during that period but could be stripped of them should he be found guilty. He has always denied the allegations and even released a statement in anticipating of the USADA’s announcement.

He went on the offensive again this morning, challenging the USADA through his Twitter account to provide him with the information he says he needs to respond to their actions.

Speaking to them on the social networking site, the Texan said: "Dear @usantidoping - we have now sent you THREE letters requesting all the relevant info in order for me to respond to your "review board".

"Until now there has been no response, not even an acknowledgement of receipt. The knife cuts both ways - it's time to play by the rules."

Armstrong survived testicular cancer early in his career and went on to win seven consecutive Tour de France titles from 1999 to 2005 while competing for the US Postal Service team and the Discovery Channel team.

He retired after the 2005 Tour de France, but returned in 2009, riding for Astana Cycling and RadioShack before retiring for a second time in February 2011, taking up triathlon earlier this year.

USADA could not be contacted by Press Association Sport this morning and had yet to issue a response to Armstrong’s Twitter question.