Space shuttle Atlantis was hauled to the launch pad early Wednesday, a major step toward a mission to resume construction of the international space station for the first time in three years.

The pre-dawn trip to the launch pad was delayed twice this week because of stormy weather.

The four-mile trek from the Vehicle Assembly Building started shortly after 1 a.m. EDT and took under eight hours.

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In the next few days, fuel and power lines will be hooked up to the vehicle, the shuttle's auxiliary power units will be test-fired and cargo will be loaded onto the shuttle.

Next week, Atlantis' crew arrives at the Kennedy Space Center for a week of dress rehearsals that include a practice launch countdown, an exercise to practice escaping from the launch pad and instruction on using emergency equipment.

Atlantis hasn't flown since October 2002, and there has been no construction on the international space station since December 2002.

During the 11-day mission, Atlantis' six astronauts are scheduled to conduct three spacewalks and deliver and install a 35,000-pound addition with giant solar arrays that power the space station.

The deadly Columbia accident in early 2003 halted all expansion of the orbiting space lab and forced a reduction in the crew size from three to two.

The crew size returned to three members last month after space shuttle Discovery delivered European Space Agency astronaut Thomas Reiter to the international space station.

The window for launching Atlantis starts Aug. 27 and lasts until Sept. 13, but NASA managers are considering opening up the window a day earlier.

NASA managers are wary of launching the shuttle too late in the window since a Russian Soyuz vehicle with three crew members is scheduled to launch from Kazakhstan on a trip to the international space station in mid-September.

Atlantis' launch will be the second of the year, and only the third shuttle mission since the Columbia disaster killed seven astronauts.