Winds crossing a runway at the Kennedy Space Center -- where the shuttle would land in case of emergency following lift-off -- exceeded the permitted rate of 15 knots, a NASA spokesman said.

Earlier in the day, NASA had given an 80 percent chance of strong winds and a storm at launch time, 3:52 p.m. (1952 GMT), following a postponement on Monday, also due to strong winds.

Atlantis is now scheduled to blast off at 3:27 p.m. (1927 GMT) Wednesday, when better weather is forecast. If a Wednesday lift-off also fails, the mission would be delayed until May because the Kennedy Space Center has other missions scheduled in the meantime.

The shuttle is to take seven astronauts to the International Space Station (ISS) to prepare it to join the Russian service module Zvezda in July, and to load it with equipment for use by crews arriving later in the year.

After a lift-off of about eight minutes, the shuttle would take two days to reach the space station and dock at an altitude of 300 kilometers (185 miles).

The mission will feature a six-hour space walk in which two astronauts, Jeffrey Williams and James Voss, will install a crane and security rails to the exterior of the station, also repairing an antenna.

They will also lock down another crane that was incorrectly attached during a mission last June.

Members of the team, which includes the Russian Yuri Usachev and two female cosmonauts, will then enter the space station through an airlock to make repairs and leave about a tonne of material on board for use by future missions.

Usachev is one of the cosmonauts slated to work aboard the ISS when construction is completed in 2001.

Assembled in December 1998, the space station so far comprises two modules -- a US section known as Unity, and the Russian module Zarya.

The Atlantis crew's most urgent task is to replace four of the Russian module Zarya's six batteries, installing equipment including ventilators after an earlier mission to Zarya had experienced nausea due to poor air circulation.

Among other items the astronauts will take to the station is a treadmill for exercises to combat the effects of weightlessness on the human body.

Atlantis will also move the space station's orbit 30 kilometers (20 miles) further from the earth, repositioning it for the docking of the Russian service module Zvezda, scheduled for July.