Cape Canaveral (Florida), Aug 26 (DPA) US space agency NASA scuttled what would have been its second attempt to launch space shuttle Discovery on a mission to the orbiting International Space Station (ISS).

After the risk of lightning forced an overnight launch to be postponed early Tuesday, the blast off was rescheduled for 1.10 a.m. (0510 GMT) Wednesday.

But hours before the new launch attempt, shuttle programme managers late Tuesday announced another cancellation after discovering a problem with a liquid hydrogen fill-and-drain valve in Discovery's aft compartment.

Launch controllers had tried to close the valve, but the device did not deliver electronic confirmation of its closure. Technicians are evaluating whether the valve could be open or partially open.

No new date was immediately set for Discovery to be launched from Kennedy Space Centre in Cape Canaveral, Florida.

The risks for Discovery's seven astronauts and the shuttle were too high Tuesday, NASA Director Pete Nickolenko said.