Lance Armstrong laments 'difficult few weeks'

(CNN) -- Potentially on the verge of losing his most prized cycling medals, and already shedding sponsors who gave him enormous wealth, Lance Armstrong said Sunday it's been "an interesting and at times very difficult few weeks."

Speaking to participants in his cancer-fighting foundation's annual Ride for the Roses, Armstrong said, "People ask me a lot how are you doing. And I tell them I've been better, but I've also been worse."

In his brief remarks to a crowd in Austin, Armstrong didn't mention the recent finding by the U.S. Anti-Doping Agency (USADA) of overwhelming evidence that Armstrong was involved as a professional cyclist in "the most sophisticated, professionalized and successful doping program." Armstrong has denied the accusations for years and attacked those who said he took part in doping - including fellow cyclists.

He stepped down last week as chairman of the Lance Armstrong Foundation, but said he will continue to be involved. Some of the foundation's donors are furious over the scandal, and want their money back.

"We will not be deterred," Armstrong said Friday night at the organization's 15th anniversary celebration in Austin, Texas. "We will move forward."

The USADA has called for Armstrong to lose his seven Tour de France titles. The International Cycling Union, which has the authority to strip him of those titles, plans to respond Monday.