"He was wrong, he cheated and there was no excuse for what he did," Fahey said by telephone in Australia.
If Armstrong "was looking for redemption," Fahey added, "he didn't succeed in getting that."
USADA chief Travis Tygart, who pursued the case against Armstrong when others had stopped, said the cyclist's confession was just a start.
"Tonight, Lance Armstrong finally acknowledged that his cycling career was built on a powerful combination of doping and deceit," Tygart said. "His admission that he doped throughout his career is a small step in the right direction. But if he is sincere in his desire to correct his past mistakes, he will testify under oath about the full extent of his doping activities."
Livestrong issued a statement that said the charity was "disappointed by the news that Lance Armstrong misled people during and after his cycling career, including us."
"Earlier this week, Lance apologized to our staff and we accepted his apology in order to move on and chart a strong, independent course," it said.
The interview revealed very few details about Armstrong's performance-enhancing regimen that would surprise anti-doping officials.
What he called "my cocktail" contained the steroid testosterone and the blood-booster erythropoetein, or EPO, "but not a lot," Armstrong said. That was on top of blood-doping, which involved removing his own blood and weeks later re-injecting it into his system.
All of it was designed to build strength and endurance, but it became so routine that Armstrong described it as "like saying we have to have air in our tires or water in our bottles."
"That was, in my view, part of the job," he said.
Armstrong was evasive, or begged off entirely, when Winfrey tried to connect his use to others who aided or abetted the performance-enhancing scheme on the USPS team