Agency officials gave him until Wednesday to make the decision on whether to talk to them under oath. They said it's the only way the disgraced cyclist could have his lifetime ban from the sport reduced.
Armstrong's attorney said the cyclist wouldn't participate in a process that "demonizes selected individuals while failing to address the 95 percent of the sport over which USADA has no jurisdiction."
Armstrong has said he is willing to help in an international effort to clean up cycling.
For more than a decade, Armstrong denied using performance-enhancing drugs. But last year, USADA released a report that detailed extensive doping and stripped him of his Tour de France victories. In an interview with Oprah Winfrey last month, Armstrong finally admitted that he doped to win those races.
The Associated Press contributed to this report.