"I made my decisions. They're my mistake. And I'm sitting here to acknowledge that and to say I'm sorry... I view this situation as one big lie I repeated a lot of times," Armstrong said, calling himself "flawed".
The fallen cycling hero said he justified his actions in the years he won the Tour from 1999 to 2005 because doping was then part of the sport's culture. He did not see it as cheating, he said.
"I viewed it as a level playing field."
Describing his favoured "cocktail" of EPO, blood transfusions and testosterone, he recalled telling himself his history of testicular cancer justified it.
He also admitted he bullied those who did not go along with him but denied forcing teammates to dope. He also denied doping during his comeback in 2009-10.