Russian cosmonaut Yury Malenchenko and US astronaut Edward Lu arrived at the Baikonur cosmodrome in Kazakhstan to complete their training and inspect their Russian-made Soyuz spacecraft, the Interfax news agency reported.

The two-man crew is due to blast off from Saturday for a six-month mission to the rotating space station, Interfax said, quoting Russian space officials.

Alexander Kalery of Russia and American Michael Foale have also been training as a replacement crew at the Star City astronaut training centre outside Moscow.

After the Columbia space shuttle disintegrated on February 1, killing all seven crew, NASA halted all planned flights to the ISS.

Russia's spacecraft are now the only means of transporting crew and supplying the space station.

Two US astronauts and one Russian cosmonaut arrived on the ISS for a four-month mission in early December.

Kenneth Bowersox, Donald Pettit and Nikolai Budarin were due to return to earth in March, but their mission was extended amid uncertainty following the Columbia disaster.

Moscow admitted this month that it would have to fund extra flights to the ISS following the US decision to ground its shuttle program, earmarking an additional 1.2 billion rubles (38 million dollars, 35 million euros) for the space program.

In part to cut down on spending, future missions to the ISS will comprise two, instead of three, astronauts.

SPACE.WIRE