Washington  - The space shuttle Discovery undocked from the International Space Station after delivering supplies and equipment to boost the capacity of the orbiting laboratory.

Pilot Kevin Ford backed Discovery away from the station at 1926 GMT for the trip back to Earth. The shuttle is scheduled to land at Kennedy Space Centre in Florida on Thursday.

The shuttle then flew around the station, allowing astronauts one last chance to examine the craft for any damage.

The crew of six US and a Swedish astronaut brought a new sleeping compartment and a treadmill named after the star of Comedy Central's Stephen Colbert, as well as two "racks" for scientific experiments and a freezer to store experiments set to be sent back to Earth. One of the racks will be used to conduct research on metals, semiconductors, crystal, glass and other materials in microgravity. The other will be used to study liquids and gels in space.

During three spacewalks, astronauts removed an empty ammonia tank and installed a new one and made other repairs.

US astronaut Nicole Stott was also delivered as the newest long- term ISS crew member, replacing US astronaut Tim Kopra, who is returning home aboard Discovery.

Discovery's mission comes as NASA attempts to complete the orbiting laboratory before the space shuttle programme's scheduled end next year.

After Discovery, only six shuttle missions remain before NASA retires its flights to the ISS by the end of 2010. It is developing a new moon-bound spacecraft called Orion, which could be ready by 2015 for trial flights. In the meantime, US astronauts will have to rely on Russia's Soyuz craft to travel to and from the ISS.

On Tuesday, a panel tasked with reviewing the US manned space programme said NASA should extend those shuttle flights into 2011 to avoid unsafely rushing to complete ISS construction. The report, ordered by US President Barack Obama, stressed the need for more money to allow humans to explore beyond low-Earth orbit. dpa