The person spoke on condition of anonymity because the interview is to be broadcast Thursday on Winfrey's network.
Armstrong was stripped of all seven Tour titles last year in the wake of a voluminous U.S. Anti-Doping Agency report that portrayed him as a ruthless competitor, willing to go to any lengths to win the prestigious race. USADA chief executive Travis Tygart labeled the doping regimen allegedly carried out by the U.S. Postal Service team that Armstrong once led, "The most sophisticated, professionalized and successful doping program that sport has ever seen."
After a federal investigation of the cyclist was dropped without charges being brought last year, USADA stepped in with an investigation of its own. The agency deposed 11 former teammates and accused Armstrong of masterminding a complex and brazen drug program that included steroids, blood boosters and a range of other performance-enhancers.
(Copyright 2013 The Associated Press. All rights reserved.)