Lance Bass of 'N Sync is competing with a former NASA official for the next seat on a Russian spacecraft.
Dmitry Malashenkov, spokesman for Russia's Institute of Biomedical Problems, said Tuesday that Bass and ex-NASA employee Lori Garver were undergoing medical tests at the Moscow center to evaluate their fitness for space travel.
They must spend time in a pressurized chamber and undergo a centrifuge test to determine how their bodies would respond to the spacecraft's liftoff.
The results will be forwarded to a state commission, which will deliver a final report on both candidates' fitness, Malashenkov said.
Russia's space agency continued to express reservations, however, that a space tourist would be ready in time for October's blastoff to the International Space Station — primarily because of the complicated contract negotiations.
But the agency will hold one seat in the three-person Soyuz spacecraft open alongside Russian flight commander Sergei Zaletin and European Space Agency astronaut Frank DeWinne of Belgium for as long as possible, space agency officials said, according to Interfax news agency.
Bass, 23, reportedly has secured the support of the a Los Angeles TV production company, Destiny Productions, to help fund his bid, and film the training and trip for a TV special.