US space shuttle Discovery was prepared for launch on Wednesday on a mission to finish installing the International Space Station's power system and deliver Japan's first live-aboard crew member.
Blastoff was scheduled for 9:20 pm EDT (0120 GMT Thursday) from the Kennedy Space Center in Florida. Meteorologists predicted a 90 percent chance the weather would be good for launch.
The mission has been delayed a month due to safety concerns about fuel pressure gauges, but after extensive testing and studies, managers cleared the ship for flight.
The shuttle is to spend two weeks in orbit to deliver a $300 million set of solar wing panels and a new distiller for the station's urine recycling system.
The panels are inside a 16-tonne module that will complete the station's 11-segment exterior backbone.
The seven-man crew includes Japan's Koichi Wakata, a two-time shuttle veteran who will stay behind on the space station to serve as a flight engineer after the shuttle departs. He replaces NASA astronaut Sandra Magnus, who has been in orbit since November.
The station, a $100 billion project of 16 nations, has been under construction 220 miles (350 km) above Earth for more than a decade. The U.S. space agency has up to nine flights remaining to complete assembly, as well as a final servicing call to the Hubble Space Telescope, before it retires the shuttle fleet next year.