The US is planning to shoot down a malfunctioning spy satellite due to hit Earth in March, senior US officials have said.
James Jeffries, the deputy national security adviser, said on Thursday that George Bush, the US president, had ordered the satellite to be shot down because it contains toxic fuel and he was "concerned about human life".
The US is planning to hit the satellite, which spun out of control after launch in December 2006, by firing a modified missile from a naval ship before it enters the Earth's atmosphere.
It would be the first time the US has used a tactical missile to shoot down a spacecraft, officials said.
Health concerns
Shooting down a satellite is particularly sensitive because of controversy over China's anti-satellite test last year, when Beijing shot down one of its own defunct weather satellites.
The move led to criticism from the US and other countries because of the amount of debris created from the explosion.
About half of the 5,000lb spacecraft is expected to survive its descent through the atmosphere. The debris could then scatter across several hundred miles.
The satellite also includes about 1,000lb of a highly toxic propellant called hydrazine, which can be harmful to the human central nervous system and can even be fatal in large doses.
Additionally, there are concerns that some of the satellite's equipment may fall into the wrong hands.
"We are worried about something showing up on eBay,'' defence and intelligence expert John Pike told AP.
The decision over how and when to shoot the satellite down will involve several agencies, including the National Security Agency, the department of homeland defence and the US state department.