There are two distinct versions of the operation mounted by the US Navy to shoot down a crippled military satellite over the Pacific. The official version, expounded in mind-numbing detail by Pentagon officials yesterday, is that the US had no choice but to launch a missile to bring down the satellite. It had been out of control since its launch 13 months ago. If not brought down, it risked crashing unpredictably to Earth, where its tank of toxic fuel would have made it a major environmental hazard.

A supplementary argument, not broached by the Pentagon, was that the military technology loaded on to the satellite was not anything that America wanted another country to find on its territory. Be that as it may, it made complete sense for the US to destroy the errant satellite before it crashed. The highly precision operation, with a window of only 10 seconds for the missile-launch, appears to have gone according to plan.

The other interpretation of the mission is not incompatible with the first but far more worrying. While acknowledging that the satellite was in trouble and a missile strike was one way of dealing with it, this version has it that the operation was in fact a covert test of a space weapon. Such tests were outlawed by the US-Soviet Anti-Ballistic Missile treaty of 1972. By abrogating the treaty in one of his first acts as President, George Bush opened the way for tests of the "son" of Reagan's "Star Wars".

Since then, the US has conducted a series of experiments in which missiles have been launched to intercept other missiles, with varying degrees of success. That the latest target was a satellite rather than another missile has led some to argue that it was merely a repetition of a test the US conducted in the 1980s, rather than anything new or more threatening. There are, however, several key differences. The satellite was out of control, and the missile used was the very latest, super-sophisticated SM-3. The biggest difference of all, however, is the existence of a potential challenger to the US in its efforts to dominate space.

A year ago, China surprised America when it shot down a satellite at a very high altitude. It was the most glaring demonstration yet of China's steady rise as a military power. It is hard not to regard this week's show of missile prowess by the US as directed towards China. Beijing, for one, was in no doubt that this was so.

Until now, US apprehension about China has tended to express itself in nonsensical panic about North Korea. This week's operation in the Pacific suggests that the proxy war is ending. Can it then be long before the US and China square up openly to compete for control of outer space?