WASHINGTON: Lance Armstrong stepped down as chairman of his Livestrong cancer charity Wednesday as Nike broke all ties with the disgraced cycling star over “seemingly insurmountable evidence” of doping.

Both developments came as the International Cycling Union (UCI) faced growing pressure to reveal how the 41-year-old, seven-time Tour de France champion had been able to escape detection for doping for so long.

In a statement on Livestrong's website, cancer survivor Armstrong said he would “conclude my chairmanship ... to spare the foundation any negative effects as a result of controversy surrounding my cycling career.

Separately, sportswear giant Nike - a major sponsor that had stuck firmly by Armstrong for months in the face of doping allegations - issued a statement that accused him of years of deception.

“Due to the seemingly insurmountable evidence that Lance Armstrong participated in doping and misled Nike for more than a decade, it is with great sadness that we have terminated our contract with him,” it said.

It added: “Nike plans to continue support of the Livestrong initiatives created to unite, inspire and empower people affected by cancer.”Livestrong is one of the best-known cancer charities in the United States, having raised nearly $500 million since it was founded by Armstrong in 1997 as he recovered from testicular cancer.

Its iconic yellow wristband was launched in 2004 in collaboration with Nike.

Armstrong always maintained he did not use banned substances, but in August he chose not to contest charges put forward by the US Anti-doping Agency (USADA) that he was a serial drugs cheat.

Last week the USADA, in a report supported by more than 1,000 pages of evidence, alleged that Armstrong was at the heart of what it called the biggest doping conspiracy in sports history.

“Lance Armstrong did not merely use performance-enhancing drugs. He supplied them to his teammates,” it said. “He was not just a part of the doping culture on his team. He enforced and re-enforced it.”Evidence included testimony from 11 of Armstrong's former US Postal cycling teammates, an expert's finding that Armstrong blood changes indicated doping and documents showing a payment to doping-linked doctor Michele Ferrari.

“The evidence of the US Postal Service Pro Cycling Team-run scheme is overwhelming,” USADA chief executive Travis T. Tygart said.

“The evidence shows beyond any doubt that the US Postal Service Pro Cycling Team ran the most sophisticated, professionalized and successful doping program that sport has ever seen.

”Although fingers have pointed at Armstrong for years, the UCI, cycling's governing body, has never sanctioned him and it has since been suggested that some officials looked the other way.

Legal experts have said the sheer and unprecedented volume and detail of the USADA allegations could lead US prosecutors and companies to consider fresh criminal and civil actions.