Premier Jay Weatherill said the state government had previously received legal advice that it could not demand the American return his appearance fees, understood to be several million dollars.

But following reports that Armstrong has confessed to using performance-enhancing drugs and that he is willing to return US taxpayer funds which went to his team, Mr Weatherill said the state government was "more than willing" to ask for its money back.

"Mr Armstrong has deceived the cycling community around the world and many South Australians will feel they were deceived by him," Mr Weatherill told reporters on Tuesday.

"We'd be more than happy for Mr Armstrong to make any repayment of monies to us."

The Associated Press reported that Armstrong, in an interview with US television celebrity Oprah Winfrey on Monday (Tuesday AEDT), had confessed to using performance-enhancing drugs to win the Tour de France.

Armstrong was stripped of all seven tour titles last year following a voluminous US Anti-Doping Agency report that portrayed him as a ruthless competitor, willing to go to any lengths to win the prestigious race.

USADA chief executive Travis Tygart labelled the doping regimen allegedly carried out by the Armstrong-led US Postal Service team as "the most sophisticated, professionalised and successful doping program that sport has ever seen".

The agency cited 11 former teammates and accused Armstrong of masterminding a program that included steroids, blood boosters and a range of other performance-enhancers.

After retiring from professional cycling following his seventh tour win, Armstrong launched his much-publicised racing comeback at the Tour Down Under in 2009 and also competed in the event the following two years.

The SA government has never detailed just how much he was paid for his appearances, which dramatically increased national and international interest in the race.

Mr Weatherill said the government would continue to keep the figure secret as disclosing the amount would reveal to others just how much the government was prepared to pay in support of major events.