NASA called off the launch of space shuttle Discovery for a second time after a crucial fuel valve failed to work properly.
Officials at Cape Canaveral halted the countdown midway through the fueling process. The seven astronauts had not yet boarded for the flight scheduled for early today and bound for the International Space Station.
Another attempt is not expected before Friday.
The valve worked fine during the first launch attempt, but thunderstorms prevented Discovery from blasting off early Tuesday morning.