BEIJING - An upgraded carrier rocket has completed assembling and is ready for China's first manned space docking due between June and August this year, an official with the China Academy of Launch Vehicle Technology said Saturday.

The carrier rocket, a modified model of the Long March-2F, is designed with a higher degree of reliability and equipped with more advanced positioning software to ensure more precise entry into the orbit, said Liang Xiaohong, deputy head of the academy affiliated to China Aerospace Science and Technology Corporation.

"Engineers with the academy have made modifications on the rocket to offer astronauts a safer and more comfortable journey to the space," said Liang, who is attending the annual session of National Committee of the Chinese People's Political Consultative Conference (CPPCC), China's top political advisory body.

China plans to launch its manned Shenzhou-9 spacecraft between June and August this year, and then conduct a space rendezvous and docking mission with the orbiting Tiangong-1 space lab module, a spokesman for China's manned space program said last month.

The space docking mission will be manually conducted by astronauts, giving China another chance to test its docking technology, the spokesman said.

Authorities have picked three astronauts for the manned docking and they have already completed their training.

One of the three Shenzhou-9 crew members will not board the Tiangong-1 space module lab, but will remain inside the spacecraft as a precautionary measure in case of emergency.

China launched the Tiangong-1 in September last year and completed the country's first-ever space docking with the unmanned Shenzhou-8 spacecraft in November.