Daisuke Enomoto had been due to blast off for the International Space Station on September 14, but it now looks like he may be replaced by an Iranian-born American.
"On August 21, the Main Medical Commission made the decision that Daisuke Enomoto was medically unfit to fly to space," the Russian agency said on its Web site. "A new crew for the 14th ISS mission will be determined in the next few days."
The backup crew comprises Peggie Whitson, a member of Expedition 5 in 2002, and Yury Malenchenko, ISS expedition 7 commander. Tehran-born Anousheh Ansari, who turns 40 next year, could become the first woman space tourist.
Three other tourists have flown to the ISS for a reported $20 million each. The first was U.S. businessman Dennis Tito, who was followed by South African Mark Shuttleworth and American Greg Olsen.
