The long-awaited decision has left cycling facing its "greatest crisis" according to UCI president Pat McQuaid and has destroyed Armstrong's last hope of clearing his name.
"Lance Armstrong has no place in cycling. Lance Armstrong deserves to be forgotten in cycling," McQuaid told a news conference as he outlined how cycling, long battered by doping problems for decades, would have to start all over again.
"The UCI wishes to begin that journey on that path forward today by confirming that it will not appeal to the Court of Arbitration for Sport and that it will recognise the sanction that USADA has imposed.
"I was sickened by what I read in the USADA report."
On Oct. 10, USADA published a report into Armstrong which alleged the now-retired rider had been involved in the "most sophisticated, professionalized and successful doping program that sport has ever seen".
Armstrong, 41, had previously elected not to contest USADA charges, prompting USADA to propose his punishment pending confirmation from cycling's world governing body.
Former Armstrong team mates at his U.S. Postal and Discovery Channel outfits, where he won his seven successive Tour titles from 1999 to 2005, testified against him and themselves and were given reduced bans by the American authorities.
"It wasn't until the intervention of federal agents...they called these riders in and they put down a gun and badge on the table in front of them and said 'you're now facing a grand jury you must tell the truth' that those riders broke down," McQuaid added.
Armstrong, widely accepted as one of the greatest cyclists of all time given he fought back from cancer to dominate the sport, has always denied doping and says he has never failed a doping test.
He said he had stopped contesting the charges after years of probes and rumours because "there comes a point in every man's life when he has to say, 'Enough is enough'".
WIDESPREAD DOPING
McQuaid, who faced criticism from several quarters for his and the UCI's handling of the affair, said he would not be resigning.
"Cycling has a future. This is not the first time cycling has reached a crossroads or that it has had to begin anew," he said in front of a packed room full of journalists and television cameras.
"When I took over (as president) in 2005 I made the fight against doping my priority. I acknowledged cycling had a culture of doping. Cycling has come a long way. I have no intention of resigning as president of the UCI.
"I am sorry we couldn't catch every damn one of them red handed and throw them out of the sport."
Other issues such as the potential re-awarding of Armstrong's Tour titles and the matter of prize money will be discussed by the UCI Management Committee on Friday.
Tour director Christian Prudhomme has said he believes no rider should inherit the titles given doping was so widespread among the peloton at the time but McQuaid made it clear the decision rested with his organisation, not the Tour.
USADA charged five people over the doping ring. Doctors Luis Garcia del Moral and Michele Ferrari and trainer Pepe Marti have been banned for life while Armstrong's mentor Johan Bruyneel has chosen to go to arbitration along with doctor Pedro Celaya.
Armstrong's last hope that the UCI might not ratify USADA's ruling sprang from long-running dispute between the two bodies over who should handle the case.
In statements issued at the news conference, the UCI continued the feud with USADA despite ratifying its decision.
"Even apart from any discussion on jurisdiction, it would have been better that the evidence collected by USADA had been assessed by a neutral body or person who was not involved in collecting the evidence and prosecuting the defendant," it said.
"This would have avoided both the criticism of a witch hunt against Mr Armstrong and the criticism that the UCI had a conflict of interest."
The UCI also said it had dope tested Armstrong 218 times and the fact he never tested positive and "beat the system" means that other organisations such as the World Anti-Doping Agency should share the responsibility of accepting the results.
USADA chief Travis Tygart issued a statement approving of the UCI's action but warning that more needed to be done.
"Despite its prior opposition to USADA's investigation into doping on the U.S. Postal Service cycling team and within the sport, USADA is glad that the UCI finally reversed course in this case and has made the credible decision available to it," he said.
"This determination to uphold USADA's decision on the U.S. Postal Services case does not by itself clean up cycling nor does it ensure the sport has moved past the obstacles that allowed doping to flourish in the age of EPO and blood transfusions.
"For cycling to truly move forward and for the world to know what went on in cycling, it is essential that an independent and meaningful Truth and Reconciliation Commission be established so that the sport can fully unshackle itself from the past."
In recent years the Tour de France and cycling had looked to be winning the battle against dopers but when asked if the sport would one day be free of the scourge, McQuaid answered: "No."
The International Olympic Committee (IOC) said it would take its time to digest the news amid suggestions that Armstrong could be stripped of his 2000 Sydney Olympics time trial bronze.
"We will study UCI's response to the USADA report and await to receive their full decision including further potential sanctions against Lance Armstrong as well as regarding any ramifications to his case," an IOC official said.
