Image from NASA video.

NASA has postponed Sunday's scheduled liftoff of the space shuttle Atlantis for 24 hours because of a lightning strike at the launch site in central Florida.

A bolt of lightning on Friday hit a wire attached to a tower that is used to protect the shuttle from such strikes, the space agency said.

Engineers announced on Saturday that they needed more time to determine whether the lightning caused any damage to the shuttle or other equipment.

On Friday, NASA said there was a 40 per cent chance that unfavourable weather would prevent Atlantis from taking off from Cape Canaveral as planned at 4:30 p.m. ET. By Saturday, the agency had revised that to 60 per cent.

ISS assembly work

During an 11-day mission, the shuttle's six-member crew, including Canadian Steve MacLean,is to resume construction of the International Space Station, the first expansion in four years.

The shuttle's payload, weighing about 17 tonnes, includes a supporting truss and two solar wings that will double the amount of power at the station.

MacLean, 51, an Ottawa-born father of three, will use the Canadarm 2 to move the panels into place. He will also take part in one of three spacewalks.

With files from the Associated Press