China's lunar probe Chang'e-2 has flown 20 million kilometers from the Earth, a milestone for the country's efforts to explore deep space, defense technology authorities said on Thursday.

Chang'e-2, China's second moon orbiter that blasted off in October 2010, has made China the fourth country to be able to examine an asteroid using a spacecraft after it flew as close as 3 km to Toutatis, about 7 million km from Earth, on Dec 13.

Wu Weiren, chief designer of China's lunar probe project, said on Thursday that engineers will strive to enable the spacecraft to fly farther in space and use this opportunity to test China's monitoring and control system for deep space exploration.

China is set to launch its Chang'e-3 probe, which is expected to carry a lunar rover that will make a landing on the moon later this year, according to the State Administration for Science, Technology and Industry for National Defense.