The US military has said it hopes to smash the satellite as soon as next week - just before it enters Earth's atmosphere - with a single missile fired from a Navy cruiser in the northern Pacific Ocean.

The official Xinhua News Agency quoted Chinese Foreign Ministry spokesman Liu Jianchao on Sunday as saying the Chinese government was monitoring the situation and has urged the US to avoid causing damages to security in outer space and in other countries.

'Relevant departments of China are closely watching the situation and working out preventive measures,' Mr Liu said. Xinhua did not elaborate.

Russia also has voiced worries about the US plan to shoot down the damaged satellite, saying it may be a veiled test of America's missile defence system.

The US has insisted the plan to shoot down the satellite is not a test of a programme to kill other nations' orbiting communications and intelligence capabilities.

The Bush administration and US military officials have said the bus-sized satellite is carrying a fuel called hydrazine that could injure or even kill people who are near it when it hits the ground.

US diplomats around the world were instructed to inform other nations that the operation is meant to protect people from the satellite's blazing descent and the toxic fuel it is carrying. The diplomats also were told to distinguish the US operation from China's much criticised test last year, when it used a missile to destroy a defunct weather satellite.

Left alone, the satellite would likely hit Earth during the first week of March. About half of the 2,268-kilogramme spacecraft would be expected to survive the fall and would scatter debris over several hundred kilometres.

Known by its military designation US 193, the satellite carrying a sophisticated and secret imaging sensor was launched in December 2006. It lost power and its central computer failed almost immediately afterward. -- AP