Part of the lengthy, wing-shaped panel looked torn and crumpled in television shots from space.

NASA had called the array deployment critical to providing electricity for European and Japanese laboratories scheduled for delivery starting in December, after a massive joint that rotates another solar panel malfunctioned.

Astronauts on the station stopped unfurling the panel when they spotted the damage, but said the glinting sun had prevented them from seeing it sooner.

"It looks like the damage appeared fairly suddenly," said Pamela Melroy, commander of the space shuttle Discovery, which is docked at the station.

NASA engineers at Mission Control in Houston told the astronauts to shoot photos of the damage for study on Earth and had them partially retract the panel to take tension off the tear.

There was no immediate word on what NASA's next move would be, but officials said on Monday if there were problems with deploying the array, spacewalking astronauts who had planned to take a look at the troubled rotating joint would instead work on the solar panel.

The mishap cast a cloud over what had been a successful day for the astronauts, who earlier installed on the station the 17.5-tonne truss in which the panel was stowed. © 2007 Australian Broadcasting Corporation