(CNN) -- Lance Armstrong, the seven-time Tour de France champion, has suffered a setback in his preparations for this year's race after a stomach virus forced him to withdraw from the Circuit de la Sarthe.
The 38-year-old American, who finished 24th in the first of four stages, pulled out before the 6.8km time trial on Wednesday.
Armstrong is one of five members of the RadioShack team to have been struck by the virus
He will return to the U.S. as soon as his condition allows, the team said on its official Web site.
Armstrong is aiming to ride in the Tour of California in May and will return to Europe for the Dauphine Libere or the Tour of Switzerland before the Tour de France begins on 3 July.
Armstrong won the last of his record-breaking seven straight titles in 2005 before retiring from racing.
He returned to competitive cycling in January 2009, and finished third in last year's Tour.