Washington for now has virtual supremacy in space, with Russia having lost much of its means to compete in the field and China generally still just starting out.

The Chinese are "behind the United States and behind Russia in their ability to use space for military purposes. But they have a very serious program to build up their capabilities," Theresa Hitchens, the director of the Center for Defense Information, told AFP in an interview.

But "in 20 years, they are quite likely to be a very powerful space power," she said.

Washington said China had fired a missile to destroy an orbiting weather satellite last week, making it only the third country after the former Soviet Union and the United States to shoot down an object in space.

If the test, which according to US magazine Aviation Week and Space Technology took place on January 11, is confirmed, China could now theoretically shoot down spy satellites operated by other nations.

On Friday Washington voiced concern that the test may have scattered debris in space that could endanger the manned International Space Station or orbiting satellites.

"I think you've certainly seen, given the history of some of the events of manned space flights, that small things can cause very big problems," State Department spokesman Tom Casey said.

In addition to the issue of orbiting debris, Washington was particularly concerned the test could signal a possible arms race in space, he said.

"We don't want to see a situation where there is any militarization of space," he said.

President George W. Bush last year adopted a new space policy calling for free US action in space, rejecting any treaty on banning space weaponry and reserving the right to stop any country opposing US interests if necessary.

In December, undersecretary for arms control and international security Robert Joseph justified the rejection of a space weapons ban saying other countries could represent a threat to US satellites.

Casey said Washington had asked the Chinese for greater detail on the test to try to allay US concerns.

But Michael Krepon, a defense expert at the Henry L. Stimson Center, said the Chinese test could be meant to precede a diplomatic offensive by Beijing on negotiating a weapons ban in space.

"It could be that China decided that since the United States was obviously not going to talk about the issue of space weaponization, our new national space policy had made it very clear we were not going to ... (that) they needed to send a message and to exhibit some capability in order to drag the United States to the table," agreed Hitchens.

"Or it could mean that China is determined to go down the path to hold US satellites at risk," she warned. "It is ominous. It could well be the beginning of a new arms race in space. And that would be very dangerous."

An arms rivalry in space would look different than the traditional kind of competition, according to Krepon.

"This will be a very different kind of race, since it does not take big numbers to make a mess of space. But there will be a competition of sorts, with major space powers preparing to use diverse means to negate the use of satellites, if push comes to shove," Krepon said.

Whatever the long-term consequences, China's test was a reckless act with other satellites nearby, Hitchens said. "It's certainly an irresponsible move by the Chinese government to deliberately destroy a satellite in a heavily used orbit and to create mass quantities of space debris. That's an irresponsible act, and they are endangering a number of people's satellites," she said.

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