Washington  - The crew of the International Space Station briefly evacuated on Thursday after ground controllers determined that a piece of space junk was within range for a possible collision.

The nearly centimetre-long debris passed safely by the ISS and the all clear was given at 1645 GMT, after the crew entered a Soyuz evacuation capsule and closed the hatches in case they were required to quickly undock from the station, NASA said.

A piece of a satellite had come close enough to the station that it required astronauts to take precautions, but the information came too late for ISS to attempt to totally avoid the debris.

The crew exited the Soyuz module after the space junk had passed and they were to return to normal operations.

The ISS crew is made up of US astronauts Michael Fincke and Sandra Magnus and Russian cosmonaut Yury Lonchakov.

The US space shuttle Discovery was to have launched for a mission to the station Wednesday, but the launch has been pushed back to at least Sunday after a leak was detected in the fuel tank hours before the planned takeoff. Discovery is to deliver the last solar panel to ISS, allowing its crew to be doubled to six permanent astronauts. The shuttle is also bringing the next ISS crew member, Japanese astronaut Koichi Wakata.

US authorities estimate there are some 13,000 pieces of space junk in orbit, others say that number could be in the hundreds of thousands. Even an extremely small piece of debris could cause severe damage to satellites or the space station.