A US firm selling the spots said on Tuesday two thrill-seeking civilians, whose names are still being withheld, had agreed to shell out $20 million each for separate trips lasting eight to 10 days in orbit.

These two space tourists will not be the first - US millionaire Dennis Tito and South African technology entrepreneur Mark Shuttleworth forked out about the same amount to be launched into space in 2001 and 2002. 

Two more seats are up for sale, locking up all the spots available on Russian Soyuz rockets through 2007, according to Space Adventures, a private US firm running the trips with the Russian Aviation and Space Agency. 

When the upcoming launches were announced in June, about a dozen people had undergone medical tests for the two available flights and paid certain fees.

The successful candidates were picked largely because they pitched unique mission objectives, Space Adventures President and Chief Executive Eric Anderson said.

One of the two is a 38-year-old male Manhattan real estate developer. No details about the other were available. 

First launch in 2004

One of the space tourists will launch in the third quarter of 2004, and the other sometime in 2005. Space Adventures expected their names to be revealed sometime in January.

Most of the $20 million per-ticket cost goes to building the Soyuz rockets, which are not reusable. But the cash also helps boost Russia's space programme. 

Russia's Soyuz craft is currently the only working link to the International Space Station, after the February crash of
the Columbia space shuttle grounded NASA's shuttle fleet.