NASA rolls out Space Shuttle Atlantis

Twice thwarted from being rolled out by overnight thunderstorms earlier this week, the shuttle began an eight-hour crawl to the launch pad at 2 a.m. (0600 GMT).

Despite the delay, NASA still has plenty of time to prepare the shuttle for blastoff as early as August 27, said Kennedy Space Center spokesman Bruce Buckingham.

The mission will be the agency's first space station assembly flight since before the 2003 Columbia accident forced NASA to ground the shuttle fleet for safety upgrades.

Columbia fell apart on re-entry into the Earth's atmosphere because falling insulation foam from the external fuel tank had knocked a hole in its wing during liftoff. Seven crew members died.