Concerns are mounting that the International Space Station may have to be abandoned after attempts to repair the two onboard computers failed last night.

One of the Russian computers, made under contract by Daimler in Germany, was rebooted last night but began to crash again almost instantly and was shut down by engineers.

The computers control the Space Station's altitude and recycling systems for the oxygen and water supplies that keep the three inhabitants alive.

"Don't get up tomorrow and expect it all to be working," said Michael T. Suffredini, the Space Station programme manager, at a briefing for reporters on Thursday.

But he added that the engineers are "making good progress to resolving this issue".

The computers crashed shortly after the Space Shuttle Atlantis docked with the Space Station. If they cannot be repaired, the Space Station will have to be abandoned and may fall to Earth or drift out into space.  

The problems may be down to new wiring which is causing electrical noise and causing the crash. Early tests have failed to isolate the problem.

Currently the station's altitude is being maintained by the Shuttle's boosters but the craft has enough fuel to continue doing this only for a few more days.

The Shuttle is extending its trip to deal with the problem, a second extension since more time was needed for repairs to Atlantis.