Armstrong remains defiant

Adelaide - Lance Armstrong said Saturday he was losing no sleep despite the threat of a federal investigation into alleged doping practices casting a cloud over his stunning career.

"It has no effect on my life -- zero," said the American, who will wind down his 20-year cycling career with the Tour Down Under this week.

So far, Armstrong has been "humbled" by the public support he has received in Adelaide, he said, as well as "amazed" by Australia's reaction as the northeast of the country reels from the impact of deadly floods.

Having helped revive the troubled sport of cycling in the wake of the 1998 Festina doping scandal, Armstrong famously beat cancer before winning a record seven consecutive yellow jerseys at the Tour de France. But he now faces potential disaster thanks to the doping probe.

Allegations levelled by former team-mate Floyd Landis late last year helped spark a federal investigation into the misuse of funds by their then team, US Postal, with whom Armstrong won six of his seven yellow jerseys.

Landis, who in 2006 was stripped of his own yellow jersey triumph following a positive test on the race, admitted doping and claimed he witnessed Armstrong using and in possession of banned substances.

Since then a grand jury probing doping in professional cycling has heard from several team-mates and associates of Armstrong over several months, although no charges have been forthcoming.

Armstrong, who has often faced accusations of doping but never tested positive for banned substances, said the investigation would not cause him to lose any sleep.

"I've got five kids to raise, a foundation to lead and a sport in which I still participate and I still love," said Armstrong, who is also known for the success of his Livestrong cancer foundation.

He is scheduled to compete for his Radio Shack team in other, as yet unnamed multi-sport events this year.

Armstrong has faced claims of doping throughout his career, and even accusations of being given the protection of the International Cycling Union (UCI), a claim which the UCI has flatly rejected.

Referring to his first Tour de France victory in 1999, he added: "I suppose 1999 was the start of it all, in terms of scrutiny.

"If you're trying to hide something you're not going to keep it hidden for 10 or 12 years."

On what will be his last competitive visit to Australia, Armstrong admitted he had been impressed by the country's collective bid to support the victims hit hard by floods in Queensland and New South Wales.

Reports of traffic jams on the way in to Queensland, as the country rallies to help those in trouble, left Armstrong in awe.

"I was amazed after hearing there were traffic jams on the way in to Queensland," he added, comparing the situation to hurricane Katrina in the US.

"There were no traffic jams when hurricane Katrina hit New Orleans."