The shuttle took off at 4:44 pm (2044 GMT) despite winds of up to 50 kilometers per hour (31 miles per hour) that threatened to cause a further delay.

"It is time for you to take a ride," shuttle launch director Mike Leinbach told the crew.

"See you back here in 11 days," responded mission commander Michael Bloomfield.

The launch -- originally set for Thursday -- was delayed as crews worked to repair the leak in the system through which liquid hydrogen is pumped into the shuttle's external fuel tanks. The leak was discovered as the tanks were being filled in preparation for Thursday's scheduled launch.

In compliance with new security regulations, the new launch time was set less than 24 hours in advance to minimize the risk of possible terrorist acts.

Workers over the weekend completed the repair work on the ground system hydrogen vent line leak, and performed a series of pressure checks, cold shock and X-ray inspections to verify the integrity of the system.

The leak, which occurred in a vent pipe on the side of the mobile launcher, is believed to have resulted from a weld that failed, officials of the US space agency NASA said.

The shuttle is carrying the first component of a future space train -- a metal girder section designed to support tens of tonnes of equipment, solar panels and other systems necessary to survival in orbit.

The astronauts will spend the bulk of the mission assembling the Mobile Transporter, a rail system that is to carry the station's Canadian-built mechanical arm along a 91-meter (300-foot) truss when it is completed in 2004.

The structure -- the longest ever assembled in space -- will move the arm at a speed of just 91 meters (300 feet) per hour as the station travels around the Earth at 27,000 kilometers an hour (17,000 miles an hour).

Shuttle commander Bloomfield, co-pilot Stephen Frick and mission specialists Rex Walheim, Ellen Ochoa, Lee Morin, Jerry Ross and Steven Smith will transport and install the railcar and the first Mobile Transporter truss segment during the mission, the 13th to the station.

Atlantis is scheduled to return to Earth on April 19.

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