The launch of the U.S. space shuttle Discovery has been rescheduled for the pre-dawn hours of Friday morning (12:22 a.m. EST/0422 GMT).

Officials with the U.S. space agency NASA rescheduled Discovery's launch late Tuesday, hours after calling off Wednesday's scheduled launch due to problems with a bad fuel valve. 

Engineers said a so-called fill-and-drain valve in the shuttle's engine compartment was not opening and closing properly.

It was the second time this week that NASA has postponed Discovery's launch.

NASA has until the end of the month to launch the shuttle.  After that, a launch would likely have to wait until October, to avoid conflicts with other flights to the space station.  The next space station mission is scheduled to come from Japan.

NASA had originally planned to launch the shuttle from the Kennedy Space Center in Florida early Tuesday, but postponed the first attempt because of stormy weather.

The seven-member crew is to deliver a new freezer and other instruments for future experiments in space.

The cargo also includes a treadmill named after American comedian and television show host Stephen Colbert, who lobbied on television to have a piece of the space station named after him.

NASA mission management chair Mike Moses said one problem engineers are continuing to watch is foam falling off the shuttle's fuel tanks during launch.  The issue has plagued several recent shuttle flights and is blamed for causing damage that led to the break-up of shuttle Columbia in 2003, killing all seven astronauts aboard.

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