The U.S. space agency NASA is struggling with bad weather as it attempts to land the space shuttle Discovery at the Kennedy Space Center in Florida.

The agency says the shuttle astronauts will try to land about an hour and a half later than previously scheduled - the new landing time is 00:40 UTC Friday.

NASA says the shuttle crew has enough supplies to remain in orbit until Sunday if necessary.

The astronauts have wrapped up a 13-day mission that included dropping off almost 8,000 kilograms of equipment at the International Space Station.

Meanwhile on Earth, NASA experts in the western state of Utah successfully test-fired a new rocket known as the Ares 1. The rocket was kept stationary as hundreds of sensors monitored thrust, roll control, acoustics and motor vibration.

The rocket is meant to be used in NASA's Constellation program, which is concerned with missions to the moon and to Mars.

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