This test does not make the case for missile defence

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Successful US 'Star Wars' test provokes anger around world

America's defence shield is back on track with a bang

One mid-air collision does not a working missile defence system make. One of the persuasive arguments against the US military's plans for a "Son of Star Wars" anti-missile shield was that it was technologically complex, hugely expensive and could never provide anything approaching certainty in its ability to shoot down incoming missiles from – generally unspecified – "rogue" states.

Yesterday's test proves only that the easiest technological issue has been resolved: that it is possible to hit a missile with another missile in mid-air or, in this case, in mid-thermosphere, at 145 miles above the Pacific Ocean. But that has been regarded as possible since before 1972, when the Anti-Ballistic Missile treaty was signed between the US and the Soviet Union – the treaty which President Bush now intends to repudiate.

It leaves all the other objections to the missile defence plan in place. It is not wrong in principle for the US, or any other country, to try to use the rapid advances in computer power and communications technologies to research the possibilities of detecting and destroying missiles. But it cannot be a sensible use of resources to try to build such a system before the more difficult technical issues of reliable detection are resolved.

Moreover, the project makes no sense without a threat assessment which suggests that stopping ballistic missiles from rogue states is a more urgent use of spending on security by the US and its allies than anything else. The fact is that nuclear, chemical and biological weapons do not have to be delivered from Iraq or North Korea to Peoria, Illinois, by rocket; they could just as easily come in the luggage hold of a commercial airliner. And the most effective way of opposing such a threat is by intelligence and the deployment of foreign policy towards outlaw regimes.

President Bush's failure to cite a specific threat lends credence to the idea that missile defence (note that the US has dropped the "national" for the purposes of promoting the plan abroad) is driven largely by the conjunction between two forces in US politics. One is isolationist public opinion, the other is the need of the famous military-industrial complex to find new things on which to spend "tax dollars" now the Cold War is over.

So far, Tony Blair has adopted the same supine posture towards those two interest groups as was adopted by Bill Clinton when he was president. When Mr Bush arrives in London this week, the Prime Minister should tell him that, while he respects the right of the US to self-defence, this scheme is an expensive and counter-productive mistake.