"Today I am disappointed for Lance and for cycling in general, that things have reached such a point that Lance has had enough and no longer wants to challenge the US Anti-Doping Agency (USADA) campaign against him," said Bruyneel.
"Lance has never withdrawn from a fair fight in his life so his decision today underlines what an unjust process this has been," he said on his website
Bruyneel was speaking hours after his friend, winner of the Tour between 1999 and 2005, dropped his challenge against the long-running campaign to prove he had used drugs while at the same time reaffirming his innocence.
The USADA has accused Bruyneel of involvement in systematic doping in his former role as sporting director of US Postal and Discovery Channel for whom
Armstrong rode when winning his seven Tour titles.
"I hope that it will soon be determined that the case that USADA initiated against me should never have gotten as far as it has," the Belgian former Tour de France stage winner added.
"Due to the sensitive nature of legal proceedings, I have been advised that it would be inappropriate for me to comment further at this stage."
In contrast, five-time Tour de France champion Bernard Hinault was unsympathetic to Armstrong's plight.
"I couldn't give a damn," the French cycling icon who won the Tour in 1978, 1979, 1981, 1982 and 1985, told ouest-france.fr. "It's his problem, not mine. This is a problem that should have been sorted out 10 or 15 years ago but which never was."
The dramatic developments late Thursday also triggered reaction from sports stars outside cycling.
Jenson Button, Formula One champion in 2009 for McLaren, wrote on Twitter: "Guilty or not the worst part is it hurts the sport of cycling."
That sentiment was echoed by Mike Tindall, the former England rugby captain and 2003 World Cup winner.
He tweeted: "The biggest loser in the Lance Armstrong affair is the sport of cycling to try and change results over the 15 years seems ridiculous".
Another England rugby international, Danny Capriani, paid tribute to Armstrong's charity work.
"Lance Armstrong could be guilty or not… The charity work he has done is amazing. Raising over $500million for cancer. Serious witch hunt!" he wrote.