Media playback is unsupported on your device Media caption Some of Hollywood's biggest names attended the Livestrong charity event

US cycling star Lance Armstrong says he has been through a "difficult couple of weeks" as he faces a catalogue of cheating allegations.

But he did not refer directly to the scandal in his first speech since the US Anti-Doping Agency named him as the central figure in a major doping ring.

The 41-year-old was speaking at a Texas event to mark the 15th anniversary of his cancer charity, Livestrong.

He maintains he is innocent, and urged supporters to keep up their work.

The US Anti-Doping Agency published a 1,000-page report last week saying he had been at the heart of "the most sophisticated, professionalised and successful doping programme" ever seen in sport.

Armstrong's lawyer has described the report as a "one-sided hatchet job".

'Not deterred'

At Friday's Livestrong event in his home city of Austin, Armstrong urged supporters of the charity to keep the work going.

"It's been a difficult couple of weeks, for me, for my family, for my friends, for this foundation," he said. "I've been better... but I've also been worse."

Since he founded the charity in 1997 - after being diagnosed with testicular cancer but before he first won the Tour de France - it has raised nearly $500m for survivors' programmes and raising cancer awareness.

Livestrong says Friday's gala event - attended by 1,500 guests including Hollywood stars Sean Penn and Robin Williams - raised $2.5m (£1.6m) for the charity.

"Thank you so much for your support, it means the world to me, to all of us," said Armstrong. "We will not be deterred, we will move forward."

He resigned as its chairman last week in an effort to distance Livestrong from his doping allegations.

Sportswear giant Nike and brewer Anheuser-Busch were among the companies who this week announced they were ending their sponsorship of Armstrong, while continuing to back his foundation.

The USADA has demanded Armstrong be banned from cycling for life and stripped of his seven Tour de France titles.

Armstrong, who lives in Austin, retired from professional sport in 2011.

On the basis of Friday's event, the cyclist still has his supporters, says the BBC's James Pearce in Texas, although these days they can be counted in their thousands rather than the tens of millions.

Those who travelled to applaud his speech left none the wiser about the lies that Armstrong appeared to tell them over the years, adds our correspondent.

He is expected to address some 4,000 cyclists at the start of the annual fundraising Livestrong Challenge race through the centre of Austin.