We must tell the US that its missile defence system is a mistake

However fervently the Blair government might wish it, the argument over America's proposed national missile defence system (NMD) will not go away. Within a few weeks, despite the disappointing results of tests so far, President Clinton is likely to give at least a partial go-ahead for the limited version favoured by his administration and whose development is likely to continue if Al Gore wins the White House.

However fervently the Blair government might wish it, the argument over America's proposed national missile defence system (NMD) will not go away. Within a few weeks, despite the disappointing results of tests so far, President Clinton is likely to give at least a partial go-ahead for the limited version favoured by his administration and whose development is likely to continue if Al Gore wins the White House.

As George W Bush's senior aides have made clear at the Republican convention in Philadelphia this week, if he becomes President he would press ahead with a much more ambitious scheme, akin to the "Star Wars" vision of Ronald Reagan. And now, after the attacks on the project from Russia and our major European allies, the Commons Select Committee on Foreign Affairs has weighed in with powerful criticism of its own, warning that the project could destabilise international relations and set off a new arms race, presenting Britain with the choice of upsetting either its most important military ally, the US, or its EU partners with whom it is attempting to forge a new defence relationship to prove its overall European bona fides.

In reality, the case for NMD is growing weaker rather than stronger. Impoverished North Korea, the rogue state against which it was primarily envisioned, suddenly looks a good deal less roguish after its overtures to the West and the recent summit with its southern rival. The failure of the latest test in July suggests that any NMD umbrella will have gaping holes - assuming the umbrella can be made to open at all. Where nuclear weapons are concerned, 70 or 80 per cent protection is not enough. If the shield is not 100 per cent effective, forget it. Add to this Russian and Chinese threats of a massive new arms build-up if NMD goes ahead, and the drawbacks of the scheme would seem to outweigh any conceivable advantage.

Alas, Britain is impaled on the horns of a familiar dilemma. NMD is driven by the American military, and the misgivings of the State Department count for little against the reluctance of American politicians of either party to offend that establishment. Such divisions cross the Atlantic to London, where the Ministry of Defence, anxious to protect its extraordinarily close co-operation with the Pentagon, broadly favours NMD; the Foreign Office, far more aware of the risk posed by missile defence to the 1972 ABM treaty (the keystone of a generation of arms control agreements) and of other likely diplomatic fallout with Russia and the EU, is opposed.

Britain's decision amounts to the choice that its governments always hate to make, between America and Europe. Finally, that decision matters in practical terms, since NMD requires the upgrading of the existing US radar installations at Fylingdales in Yorkshire and possibly the construction of a new facility elsewhere in the UK. Small wonder the Government is unwilling to break cover before it absolutely has to.

But the Select Committee is right. Precisely because of the intimate defence links between the two countries, precisely because of the Fylingdales connection, ours is perhaps the only friendly foreign voice that will carry weight in Washington. Politely, privately if necessarily, but emphatically, that voice should be telling the Americans that with national missile defence they are making a huge and unnecessary mistake.