Lance Armstrong's attorney has confirmed that the disgraced cyclist has decided not to speak under oath to US Anti-Doping Agency officials.
Armstrong has been given a lifetime ban from sports after a USADA report last year revealed extensive doping on his Tour de France winning teams.
The 41-year-old American was stripped of his seven Tour de France titles and subsequently admitted to doping during a televised interview with Oprah Winfrey last month.
He was informed his life ban from sports would only be reduced if he testified under oath to the USADA about his past and, having initially been given until 7 February to confess, he was granted a two-week extension, prompting speculation that an agreement was close.
However, although Armstrong has said that he is keen to help clean up the sport, he has decided against speaking under oath about doping.
Armstrong's lawyer Tim Herman said in a statement: "Lance is willing to cooperate fully and has been very clear: He will be the first man through the door, and once inside will answer every question, at an international tribunal formed to comprehensively address pro cycling, an almost exclusively European sport.
"We remain hopeful that an international effort will be mounted, and we will do everything we can to facilitate that result.
"In the meantime, for several reasons, Lance will not participate in USADA's efforts to selectively conduct American prosecutions that only demonise selected individuals, while failing to address the 95 per cent of the sport over which USADA has no jurisdiction."
The USADA's chief executive Travis Tygart says the agency will continue their investigation without the help of Armstrong.
"We have provided Mr Armstrong with several opportunities to assist in our ongoing efforts to clean up the sport of cycling," said Tygart.
"Following his recent television interview, we again invited him to come in and provide honest information, and he was informed in writing by the World Anti-Doping Agency (WADA) that this was the appropriate avenue for him if he wanted to be part of the solution.
"Over the last few weeks he has led us to believe that he wanted to come in and assist USADA, but was worried of potential criminal and civil liability if he did so.
"Today we learned from the media that Mr Armstrong is choosing not to come in and be truthful and that he will not take the opportunity to work toward righting his wrongs in sport.
"At this time we are moving forward with our investigation without him and we will continue to work closely with WADA and other appropriate and responsible international authorities to fulfil our promise to clean athletes to protect their right to compete on a drug-free playing field."