NASA will wait at least a week before launching the space shuttle Endeavourafter a mysterious oxygen leak forced it to halt its countdown for an early morning liftoff.
The shuttle was set to ferry a new crew to the International Space Station and a 19-tonne frame segment for the growing outpost.
But the flight was cancelled late last night about three hours before liftoff, just as the commander, Capt James Wetherbee, was being strapped into his seat.
Endeavourwill sit for seven days as engineers pick their way through its insides. They will be looking for the cause of a pound-per-minute leak in a system that supplies oxygen to the crew's space suits during launch and landing, and to the crew cabin while in orbit.
NASA's shuttle programme chief, Mr Ron Dittemore, said the leak of pure oxygen was not enough to pose a fire risk. He said his primary concern was that the leaking system had passed its prelaunch checks but indicated a problem as soon as it was turned on.