But his team also faced fresh questions over their recruitment policy following revelations that a member of the staff worked for the notorious US Postal team and helped Armstrong to his first Tour de France victory.

Armstrong, who was stripped of his record seven Tour titles claimed from 1999 to 2005 before confessing to using performance-enhancing drugs, pointed to other convicted dopers who are still involved in professional cycling.

Chris Froome has been smart.

However Sagan is regarded as a better rider when the course becomes lumpy, as evidenced by his Tour of California win, and he was able to pick up seventeen points for netting second in the intermediate sprint. The American will surely take heart in the fact that he outgunned Froome, at least temporarily, last month during the Dauphiné.

A Sky spokesman said by e-mail: “Our zero tolerance policy is well-known and well-established – nowhere more so than within our own staff who have all been interviewed extensively about their careers before joining the team”.

Britain’s Chris Froome retained the yellow jersey a day earlier after a hot, rain-splattered stage won by Spain’s Joachim Rodriguez.

Tour de France leader Chris Froome has said he is willing to undergo physiological tests after this year’s race to put to rest any suspicion of doping.

Rodriguez made his move halfway up the final 10-mile uphill grind, wheeling around world champion Michal Kwiatkowski in a switchback, and riding alone to the finish.

The Spaniard had already won the third stage finish on the Mur de Huy and also had a stage victory back in 2010.

Sticky heat bothered the pack as it set off from Lannemezan on Thursday morning.

The 195-kilometer (121-mile) trek to the Plateau de Beille, which draws cross-country skiers when it snows, took the Tour up four increasingly high ascents, 53 kilometers (33 miles) in total.

“I can understand that there’s still some hurt feelings”, Armstrong told reporters Thursday. Tour racers were largely indifferent, and Armstrong’s presence wasn’t felt at the race itself. “My job is to come here, stay calm and answer all the questions”. “I am not a specialist”. “If you’re leading the Tour by three minutes, that’s impressive”.

Many seasoned race observers say it will take almost a miracle for Froomes main rivals to topple him before the race ends on Paris Champs-Elysees on July 26.

Froome fought off challenges by Alberto Contador and Nairo Quintana to remain comfortably in first place ahead of Tee-jay van Garderen. “If that were the rule, the caravan would nearly be empty”, Armstrong said.

Armstrong is taking part in Geoff Thomas’s “One Day Ahead” operation and will join former England footballer Thomas and a team of amateurs, who are aiming to raise one million pounds ($1.57 million) for Cure Leukaemia, by cycling in two stages a day before the official peloton goes through.