Graphic on China's unmanned spacecraft Shenzhou VIII, which will be launched Tuesday to dock with the Tiangong-1 experimental space lab put into orbit in September.

China said Monday it will launch an unmanned spacecraft on Tuesday, taking its next step towards the goal of building its first space station by 2020.

The VIII will blast off from the in China's northwest at 5:58am on Tuesday (2158 GMT Monday), the state Xinhua news agency said.

It is due to join with the Tiangong-1, or "Heavenly Palace", experimental module later this year in what would be the first Chinese docking in space. If that succeeds, the module will then dock with two more spacecraft, at least one of which will be manned, in 2012.

China began its manned spaceflight programme in 1990, after it bought Russian technology that enabled it to become the third country to send humans into space, after the former Soviet Union and the United States.

It aims to finish its space station, where astronauts can live for several months, as they do on the ISS or the former Russian Mir, by 2020.

The country launched its first manned spaceflight in 2003 and sees its ambitious space programme as a symbol of its global stature.

China's Long March-2F/H rocket carrying the unmanned spacecraft Shenzhou-VIII sits on the launch pad in Gansu on October 30. The Shenzhou-VIII will conduct the country's first space docking with Tiangong-1, or Heavenly Palace-1, a space lab module which was recently launched into space, in what would be the first Chinese docking in space.

The of Tiangong-1 on September 29 -- ahead of China's National Day on October 1 -- was attended by Premier Wen Jiabao, while President Hu Jintao watched from a space centre in Beijing.

But China is playing catch-up in the space arena and the planned space docking later this year will emulate what the Americans and Russians achieved in the 1960s.

Xinhua said docking technologies were crucial to the success of China's space station ambition.

Mastering docking technology "will make it possible for China to carry out space exploration of larger scale," it quoted Zhou Jianping, chief designer of China's manned space programme, as saying.