CAPE CANAVERAL, Florida — NASA scrubbed space shuttle Discovery's first landing plan yesterday because of rain in Florida and was considering ordering a New Mexico landing, something it has done only once before.Astronaut Ken Ham in Mission Control told the crew that Kennedy Space Center still remained an option later yesterday if the weather improved.

The next opportunities are at Kennedy, Edwards Air Force Base in California's Mojave Desert, which would be NASA second choice, and at White Sands, New Mexico, starting around 5.30 p.m. In an encouraging sign, Ham told the astronauts to start drinking fluids, one of the last steps they take before landing to help them adjust to gravity.

"The winds at Edwards are becoming somewhat more favourable, and we might be able to get a position where we can forecast 'go' winds there," Ham said. "As well, the picture at the Cape is a little bit more encouraging."

Early forecasts of rain at Kennedy and crosswinds at Edwards had increased the chances that White Sands Space Harbour would be see a shuttle landing for the first time in 24 years. In the only previous landing there, by shuttle Columbia in 1982, sand on the runway contaminated the orbiter, and the brakes were damaged. The facility is normally not equipped to service the shuttles, either.

"I have a lot of things to worry about on this flight that I can control, and the weather is something I can't," Discovery commander Mark Polansky told reporters from space. "I'm ready to land at any of the three sites."

Discovery needs to be on the ground Saturday or it could run out of the fuel that powers its electrical system. NASA normally has more time for the landing, but the astronauts spent an extra day at the international space station this week to work on a stubborn solar array.

NASA managers hoped the weather would clear at one of the favoured sites, but they shipped a crane to White Sands anyway, along with equipment that purges gases and cools and heats the shuttle on the ground, thruster plugs and 60 workers from the Kennedy Space Center.

"As we get closer, we'll have much more certainty on what we're really faced with," said entry director Norm Knight, who will oversee the landing.

If the second landing plan is scrapped, a third opportunity would come around 7 p.m. at Edwards and White Sands. NASA managers were considering a last try at 8.36 p.m. at Edwards.

NASA has seven more opportunities to land the shuttle today.

Discovery originally had been scheduled to land Thursday, but the flight was extended to allow a fourth spacewalk to fold up an accordion-like solar array on the space station.

Thursday afternoon, after another inspection and more analysis of the shuttle's heat shields, the space agency pronounced Discovery safe to return. Shuttles are routinely inspected in flight now for any debris damage of the sort that doomed Columbia in 2003.

During the 25 years of the shuttle programme, there have been 63 landings at Kennedy, 50 at Edwards and just one at White Sands.

Even though the White Sands runway regularly is used for practice landings by astronauts, NASA does not like to use it for the real event. It could take as long as two months to get the shuttle back to Florida from New Mexico, compared to a week from Edwards, threatening NASA's ability to get Discovery ready to fly again next October.

Flight controllers in Houston, trying their hand at holiday songwriting, sent the Discovery crew in their daily messages lyrics to their version of the song, "Let it Snow."

"Oh, the weather at KSC is frightful. But at White Sands, it's so delightful. And since we have to land. Land White Sands. Land White Sands. Land White Sands," it said.