'A manned moon landing is a project which involves great difficulties, high risks and huge investments. Enthusiasm alone is not sufficient to launch the project,' Luan Enjie , chief commander of China's moon orbiter project, was quoted by Xinhua as saying.

Mr Luan said many factors had to be taken into account, such as budgets, technological ability, and whether it was essential to scientific research. 'It is too early to talk about manned landings on the moon.'

According to Xinhua yesterday, experts highlighted the particular difficulty with rockets.

They reportedly said that China's rockets could only carry a nine-tonne spacecraft to an altitude of 300km, and five-tonne satellites to an Earth orbit of 36,000km. The next generation of rockets being developed could boost the capacity to 25 tonnes and 14 tonnes for the respective distances, but that would require several years of work.

Aerospace engineer Zhang Qianshan said the challenge for developing the mainland's rockets was in the cargo weight they could carry rather than the distance they could travel. In a manned landing mission, a rocket only had to travel about 36,000km and the lunar module would travel the rest of the way by itself. But the weight for the rocket would be much greater.

'We would require a rocket that could fit a spacecraft, and one that could carry the weight of additional equipment, fuel and the astronauts.'

Apart from the rockets, scientists also need to crack technological problems associated with allowing astronauts to walk in space, the docking and return of spacecraft, and the survival of astronauts on the moon.

'We don't possess those technologies for now, and we cannot solve those problems in a short period of time,' lunar programme chief designer Sun Jiadong told Xinhua.

Chief moon project scientist Ouyang Ziyuan also said the need for further scientific research could only be determined after the lunar probe phase was completed, Xinhua quoted.

The plan now is to send up an unmanned rover by 2012, and deploy a robotic mission to bring back samples by 2017.

Amid speculation that China is joining the United States, Europe, Japan and India in a new space race to send astronauts to the moon, China has been keen to emphasise its 'peaceful rise'.

Nasa earlier announced a 2020 deadline for returning Americans to the moon, and predicted that China might beat that target. There have also been widespread media reports about Chinese scientists expecting to put an astronaut on the moon between 2020 and 2025. But it appears they have retreated from that position, stressing the technological difficulties they face.

Chang'e I blasted off on Wednesday at 6.05pm and successfully separated from the rocket to enter an Earth orbit at an altitude of 300km at 6.29pm.

The orbiter manoeuvred itself to an orbit 600km above the ground yesterday just before 6 pm. It will continue to circle the Earth, switching orbits several more times, before it finally begins heading for the moon on October 31.

If everything goes to plan, Chang'e I will slide into a lunar orbit on November 5, when authorities will be able to declare the launch a success. It will beam back the first images of the moon's surface in the latter half of next month.

Outward bound

A projection of the probe's path up to 48 hours into its mission, after which it will start its journey to the moon

SOURCE: XINHUA