The launch of the US space shuttle Discovery has been postponed for the second day in a row to due to poor weather at Cape Canaveral, Florida. A third launch attempt will be made on Tuesday.

With threatening storm clouds gathering and lightening detected a few miles from the launch pad, officials of the US space agency NASA said they had no choice but to scuttle Discovery's launch.

The news was relayed to the shuttle's seven-member crew after the astronauts were suited-up and strapped into their seats in preparation for lift-off.

Discovery's commander, Steve Lindsay, readily agreed with the assessment that it was not a good day for a space launch.

"Yeah, we copy," said Steve Lindsay. "We looked out the window and it doesn't look good today. And we think that's a great plan."

NASA will attempt another launch on Tuesday, weather permitting. The 48-hour delay will give engineers time to refuel and service the spacecraft.

Deputy shuttle program manager Jim Shannon says space officials do not want to rush to launch in bad weather.

"You know, nobody is going to remember that we scrubbed a day or two days a year from now," said Jim Shannon. "But if we go launch and get struck by lightening or have some other problem, that will be very memorable. Since we have taken this much time, we're going to wait until weather conditions are right and we'll launch when we are ready."

NASA administrator Michael Griffin approved the launch despite the concerns of the agency's top safety officer and chief engineer.

They recommended Discovery remain grounded while additional checks be made of foam on the fuel tank.

NASA engineers redesigned the external fuel tank after debris damaged Columbia and caused the shuttle to disintegrate on reentry into earth's atmosphere three years ago, killing the shuttle's crew.

Engineers also made modifications after last year's Discovery mission when a 0.45 - kilogram piece of foam insulation came off.

This time around, Discovery's crew will test and inspect the shuttle and various repair techniques, and deliver the European Space Agency's newest astronaut, Thomas Reiter, for a six month stint aboard the International Space Station.

If bad weather grounds the shuttle for a third time on Tuesday, NASA will try again on Wednesday.