The launch was reset for 7:40 pm Saturday (00H49 GMT Sunday), NASA spokesman George Diller said, adding that if weather in Spain still precluded a launch at that time it would be put off until Monday at the earliest.

On Friday weather forecasts were good for the Cape Canaveral, Florida, launch site, but the weather must also be acceptable over at least one of the two alternate Spanish airstrips.

Weather conditions at air strips at Moron, southern Spain, and Saragossa in the north were both unacceptable, said NASA, adding that an air base in Morocco that once served as an emergency shuttle landing site was no longer in use.

The emergency airstrips would only be used if the shuttle developped engine trouble or failed to attain sufficient altitude following liftoff.

The shuttle had been initially scheduled to blast off to the International Space Station (ISS) on November 11, but NASA put off the launch after a leak was discovered in a pipe that carries oxygen to the cabin of the spacecraft.

The shuttle's crew is to do construction work on the ISS. The shuttle is also to deliver a fresh crew of three astronauts to the ISS and bring home the current one.

SPACE.WIRE