Pre-launch tests on the Chang'e I rocket and orbiter were nearly complete and they have been transported to the launch site, the official told state news agency Xinhua.

China is also planning to land a human on the moon and make a series of robotic missions with a view to building a base there after 2020, officials have said. China earlier said it would launch the probe by the end of the year.

"The appropriate time for the launch is in April and October," Zhang Qingwei, minister of the Commission of Science, Technology and Industry for National Defence, was quoted as saying.

"We finally chose October with the consideration of weather and celestial conditions.

"China's moon exploration project is for peaceful use of space."

Advanced cameras and X-ray spectrometers have been installed in the orbiter to map three-dimensional images of the lunar surface, analysing moondust and studying the space environment between the Earth and the moon, he said.

The next step in the ambitious mission would be to launch a moon vehicle and then return it to earth, Zhang added.

The launch of the moon orbiter is part of a three-step lunar exploration programme China hopes will eventually see moon samples brought back to Earth.

China's space agency chief Sun Laiyan earlier said the three phases involved orbiting the moon, landing on the lunar surface and coming back to Earth with samples.

The orbiter represented the first phase, with a moon rover to be used in the second phase scheduled for around 2012. The plan for the third phase was for another rover to land on the moon and collect samples before returning to Earth.

China has offered 2,000 tickets to the public to view the Chang'e I launch outside the southwestern city of Xichang.

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