"We have agreed to his request for an additional two weeks to work on details to hopefully allow for this to happen."
After Armstrong admitted last month in a televised interview to using banned drugs during all of his record seven Tour de France triumphs, Tygart had given the 41-year-old Texan until Wednesday to "cooperate fully" with anti-doping authorities if he really wanted a chance to reduce his lifetime ban.
Armstrong had said he wouldn't be able to meet the deadline. He did voice a willingness to take part in any "truth and reconciliation" commission that might be put together by the International Cycling Union (UCI) and World Anti-Doping Agency (WADA).
However, Armstrong attorney Tim Herman had told USA Today this week that Armstrong didn't believe USADA was the best-placed agency to lead the battle against doping in cycling because of the sport's long European history.
Even though he had welcomed Armstrong's confession, which came after years of steadfast denials, Tygart had insisted that if Armstrong really wanted to correct his past mistakes he had to testify under oath about the full extent of his doping activities.
Tygart has also taken issue with some of Armstrong's statements to interviewer Oprah Winfrey, saying Armstrong lied when he insisted that he didn't use performance-enhancing drugs when he came out of retirement to race in 2009 and 2010.