But Armstrong has long been dogged by doping allegations, with compatriot Floyd Landis -- who was stripped of his 2006 Tour de France title after failing a drug test -- making a series of claims in 2011.
Armstrong sued the USADA last year to stop its investigation of him, arguing it did not have the right to prosecute him. But after a federal judge dismissed the case, Armstrong said he would no longer participate in the investigation.
In October 2012, Armstrong was stripped of his titles and banned from cycling. Weeks later, he stepped down from the board of his foundation, Livestrong.
It is unclear whether Armstrong would face criminal prosecution for perjury should he confess. Armstrong was involved in several cases where he gave sworn testimony that he never used banned drugs.