Russia on Monday proposed sending a Kazakh cosmonaut to the International Space Station in place of a space tourist in September after a Japanese candidate formally dropped out.

Satoshi Takamatsu, a Japanese businessman, was gearing up to go to space after signing a contract to undergo training but said Monday that he was not ready for the launch expected in early September.

"The Russian commission has proposed sending a national of Kazakhstan to the ISS," spokesman for the Russian space agency Roscosmos, Igor Burenkov, told AFP.

Burenkov said Russia had to agree the plan to send Kazakh pilot Aidyn Aimbetov into space with its ISS partners before making a formal announcement.

Takamatsu, who trained together with British singer Sarah Brightman, said he still wanted to travel to space but would wait until later.

"I will wait until the moment is right for me," Takamatsu was quoted as saying in a statement by space tourism agency Space Adventures.

He said that the art projects he wants to pursue in space require more time.

"We hope that he realises his dream of launching to space in the next two-four years," Space Adventures president Tom Shelley was quoted as saying in the statement.

Last month, Brightman, known for her roles in West End musicals such as "Phantom of the Opera," announced she had to pull out of preparations for family reasons.

Kazakh cosmonaut Aimbetov -- a 42-year-old former pilot in the Kazakh airforce who was not scheduled to blast off until 2017 -- is now likely to travel to the ISS after both Brightman and Takamatsu dropped out.

The space agency of Kazakhstan declined comment on Monday.

Aimbetov would be joining Russian cosmonaut Sergei Volkov and Andreas Mogensen of the European Space Agency, who will be the first ever Danish national to go into space.

Previous space tourists visiting the ISS on a total of eight trips have included the Canadian founder of the Cirque du Soleil, Guy Laliberte, and Iranian-American entrepreneur Anousheh Ansari, the only woman so far.

Several prospective space tourists have been rejected in the past for health reasons or failed to come up with money to finance the mission.