A spokesman for Armstrong said Thursday the U.S. Anti-Doping Agency had yet to provide documentation of the blood tests from 2009 and 2010 that allegedly indicated Armstrong was on blood-manipulation drugs in the run-up to his comeback on the Tour de France.
Armstrong is a seven-time Tour de France winner.
"The USADA has failed to respond to either of our two letters, and so the answer is yes, they are refusing at this point to turn over any evidence," Mark Fabiani, an Armstrong spokesman, told the Austin (Texas) American-Statesman.
The USADA alleged earlier this week that Armstrong, his coach and four medical personnel took part in a doping conspiracy that dated back to at least 1996. The agency, which cannot file criminal charges, is calling from a lifetime ban for Armstrong from all sports.
The Austin-based cyclist was barred from taking part in triathlons, which he has been competing in since earlier this year. The newspaper said Armstrong was in France preparing for an event when the USADA issued its letter.