"Sitting here today, dealing with all this stuff again, knowing if I were to go back, there's no way I could get a fair shake - on the roadside, in doping control, or the labs," Armstrong said on a late-afternoon conference call.
"I think it's better that way," he added a moment later. "I'm happy with the way my career went and ended and I'm not coming back."
The seven-time Tour de France champion and his handlers spent most of the remaining 45 minutes with reporters criticizing World Anti-Doping Agency chief Dick Pound.
It was Pound who set off another round of charges and counter-charges earlier Thursday by accusing cycling union boss Hein Verbruggen of supplying documents used by a French newspaper to charge that Armstrong used the blood-boosting drug EPO during his first tour win in 1999.
Armstrong, who has repeatedly denied ever using banned drugs, said he was the victim of a "witch hunt" after the report came out last month in L'Equipe, France's leading sports daily.
Armstrong said he was concerned Pound might be seeking revenge for an open letter he sent to newspapers and the WADA chief several years ago, defending his sport against the widely held notion that cycling was rife with performance-enhancing drugs.
"I was not trying to say that Dick was bad guy or a crook," Armstrong said of his letter, "but I might want to say that today. ... He's trying to divert attention from the serious ethical issues involving WADA and himself."