By Irene Klotz

CAPE CANAVERAL, Fla., July 2 (Reuters) - The U.S. space shuttle Endeavour was rolled out of a hangar on Monday and taken to an assembly building at the Kennedy Space Center to be fitted with a fuel tank and booster rockets for a scheduled Aug. 7 launch.

The shuttle and seven astronauts will be heading to the $100-billion International Space Station to install the next piece of the outpost's external frame and to deliver equipment and supplies.

It will be Endeavour's first flight since before the 2003 Columbia accident, which grounded the shuttle fleet for 2-1/2 years for safety improvements.

Endeavour's mission was originally to have been flown by Columbia, which broke up on re-entry into the atmosphere because of a hole in its heat shield.

The remaining shuttles will continue to fly only long enough to complete the station, a project of 16 nations that is around 60 percent finished. NASA has three years to complete the job.

In addition to 12 remaining space station construction missions, NASA also would like to squeeze in two shuttle flights to deliver spare parts to the station and carry out a final servicing call to the Hubble Space Telescope.

The U.S. space agency had a late start to its 2007 flight timetable.

The first mission of the year, carried out by the shuttle Atlantis to deliver new solar power panels to the space station, was delayed three months while workers repaired damage to the spacecraft's external fuel tank caused by hail.

Weather again intervened at the end of Atlantis' mission, forcing flight directors to use a backup landing site in California on June 22 because Kennedy Space Center in Florida was blanketed by clouds.

Flying piggyback on top of a modified Boeing 747 jumbo, the shuttle left Edwards Air Force Base in California on Sunday. After three stops for refueling, Atlantis is expected to arrive back at the Kennedy Space Center on Tuesday.

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