WASHINGTON, July 15 (Xinhua) -- U.S. Space shuttle Discovery undocked from the International Space Station (ISS) early Saturday, beginning the two-day trip back to Earth, according to NASA TV.

The undocking of Discovery occurred at 6:08 a.m. EDT as the two spacecraft flew above the Pacific Ocean north of New Zealand.

At about 4 a.m. EDT, the six-member Discovery crew paid farewell to the Expedition 13 crew after a nine-day stay and exited the International Space Station.

"Have a safe journey back, a soft landing and we'll see you on the ground in a few months," said U.S. flight engineer Jeff Williams of the Expedition 13 crew.

Before Discovery's undocking, both crews conducted leak and pressure checks.

After undocking, pilot Mark Kelly performed two separation burns to take Discovery away from the station.

At about 9 a.m. EDT, crewmembers will use robotic arm and the orbital boom sensor system to perform final inspections of the starboard wing and the shuttle nose cap.

Discovery will remain about 72 km behind the ISS until the mission management team reviews survey results and clears Discovery for landing.

This is the second space flight since Columbia disaster in 2003. The mission, designated STS-121, delivered a new Expedition 13 crew member and much needed supplies and equipment to the international outpost.

The shuttle crew also conducted three spacewalks to perform maintenance on the station and to test on-orbit heat shield repair techniques.

Landing is scheduled at NASA's Kennedy Space Center in Florida at 9:07 a.m. EDT Monday. Weather forecasts call for favorable landing conditions. Enditem