China plans to launch an 8-ton space laboratory within four years as a stepping-stone to grander space feats such as an eventual lunar landing, top scientists said Tuesday.

They were speaking following the successful flight of Shenzhou VII and the spacewalk.

The scientists, however, warned that astronaut Zhai Zhigang's 15-minute walk was just one step, and there will be tougher challenges ahead sending aloft a space lab by the end of 2011, setting up a space station, and ultimately a manned moon landing.

"With this successful Shenzhou VII mission, we've broken through and mastered the technology for extra-vehicular activity," Wang Yongzhi, former chief designer of China's manned space program, said.

Extra-vehicular activity is a term used for spacewalks.

The space lab will be manned for short periods and used to master complex docking and other skills needed for long-term tasks, Wang said in an interview posted on the space program's official news website (http://www.cmse.gov.cn).

Those tasks could include the moon, Wang, now a senior consulting engineer with the space program, said.

"The moon is the closest space entity to Earth, the starting point and base for pioneering the exploration of deep space, so a manned landing on the moon should be our future strategic objective," he said, according to the website.

Scientists are assessing the feasibility of a manned moon landing and will seek central leadership approval "when conditions are ripe", Wang said.

"I'm sure that in the not-too-distant future, a Chinese person will land on the moon."

China now joins Russia and the United States as the only countries able to send people into space.

But Chinese experts stressed the country's next big goals in space face major technological hurdles.

The two "tougher and more complicated" skills that still need to be mastered are docking, and learning how to keep astronauts alive and well in orbit for long periods of time, Ma Xingrui, a deputy commander of the space mission, was quoted by Xinhua News Agency as saying.

Another senior engineer told China Central Television that experts were studying docking techniques, but warned it was no easy task.

"It is like threading a needle in space," Su Shuangning said.

To send aloft the much larger space station, weighing about 20 tons, China will also need a new generation of more powerful rockets.

Technological delays have held back the building of these new rockets, now expected to come on stream about midway through the next decade, officials have said.

"China is still quite far behind the United States and Russia (in space technology)," Jiao Weixin, a space scientist at Peking University, said.

"It's unrealistic to speak of us catching up. We're just doing our best to narrow the gap with them."

(China Daily October 1, 2008)