"I think the flight does have extra meaning because of that, because of the fact that our close friends did perish just two months ago," Lu told reporters at a space training center outside Moscow.

"We of course will be thinking about them when we are up there, but that doesn't mean that we should stop what we are doing," he said. "If you stop at the first setback, you won't get anywhere."

Lu and Russian cosmonaut Yury Malenchenko are due to blast off for a six month mission on the spinning orbiter on April 26 aboard a Russian-made Soyuz rocket.

They will fly on Sunday to the Baikonur cosmodrome in Kazakhstan, where the launch will take place.

After the US Columbia space shuttle disintegrated on February 1, killing all seven crew, NASA halted all planned flights to the ISS and grounded the remaining three space shuttles.

Russia's spacecraft are now the only means of transporting crew and supplying the ISS, and Lu paid tribute to the Soviet-era program.

"The only reason we can continue this program right now is because the Russians have the capability to launch Soyuz and Progress spacecraft right now," he said. "That's very, very important.

"In general though, I do think that the international aspect of this is a very important part of the program, especially in the light of the situation in the world today," he said in reference to the war in Iraq.

"I think it's very important that we show the world what we can do together with our friends -- the Russians and the Europeans, the Canadians and the Japanese, and so on."

Kenneth Bowersox, Donald Pettit and Nikolai Budarin were due to return to earth in March, but their mission was extended following the uncertainty triggered by the Columbia disaster in which the seven astronauts aboard the US shuttle died as it disintegrated upon re-entry.

Moscow admitted for the first time this month that it would have to fund extra flights to the ISS following the US decision to ground its shuttle program.

The Russian government decided to earmark an additional 1.2 billion rubles (38 million dollars, 35 million euros) in budgetary funds to the space program over the next six months.

Future missions to the ISS will comprise two, instead of three, astronauts.

SPACE.WIRE