CAPE CANAVERAL, Florida (AP) – NASA began rolling space shuttle Atlantis off its launch pad and back into a huge assembly building yesterday as Tropical Storm Ernesto headed for Florida.

“It was about the weather and keeping the vehicle safe,” said NASA spokeswoman Tracy Young.

The move, started shortly before noon, was expected to take about 12 hours.

NASA rules say the shuttle should not be outside in winds of more than 45 mph (72 kph). yesterday morning, Kennedy Space Centre was under a tropical storm warning, meaning the area was expected to get winds between 39 mph (62.7 kph) and 74 mph (119 kph) by today.

The roll-back to the assembly building challenges NASA’s ability to launch Atlantis in September on a mission to resume construction of the international space station.

The earliest a launch attempt could take place once Atlantis is rolled back will be eight days after the shuttle is returned to the launch pad.

NASA had wanted to launch before September 7th. If it decides to attempt a launch after that date, it could interfere with Russia’s plans in mid-September to send a Soyuz spacecraft with two crew members and a space tourist to the orbiting space lab. Having both the shuttle and the Soyuz at the space station would create a traffic jam.

Atlantis’ main mission is to add a key 17 1/2-ton construction truss to the space station, including two solar wings that eventually will provide a quarter of the space station’s power.