Space shuttle Atlantis  on launch pad at Kennedy Space Center

The U.S. space agency now says it has postponed the launch of the space shuttle Atlantis until Friday.

NASA had planned to launch Atlantis Wednesday on an 11-day mission. But the launch was delayed due to a problem with a fuel cell used to provide electricity to the shuttle.

Atlantis was originally set to depart last month, but bad weather caused a series of postponements.

Space agency engineers hope to launch Atlantis this week so that long-delayed work on the International Space Station can resume. Construction stopped after the shuttle Columbia disaster in February 2003 forced a long moratorium on shuttle flights.

Failure to launch the shuttle this week could delay the mission until October.

Astronauts on the mission are expected to attach a 17-ton addition to the space station. It will include a new set of giant solar energy panels that will reach 80 meters in length when fully unfurled.

The launch schedule date is dictated by the need to avoid conflict with a planned September 14 Russian Soyuz launch with a new Russian-American space station crew.

Some information for this report was provided by AFP and AP.