Nato suffers from a terminal illness, but no one dares kill it off just yet

There is a simple rule in politics. The more politicians talk of an institution as being "relevant" and "reborn", the more you know it's on its last legs. Yesterday the air in Prague was positively tropical with the hot breath of 40 world leaders attending a summit of the North Atlantic Treaty Organisation all saying how important this venerable alliance was. What they actually meant when you listened carefully was that they all had their individual reasons for finding the organisation useful at this particular moment.

The Americans, having ignored and, indeed, deliberately marginalised the institution over the year since 11 September, now see it as a way of establishing the grand alliance to invade Iraq. The Europeans, having bravely talked of being a countervailing force to US "unilateralism", are now becoming distinctly nervous that America might go its own way and they want Nato to keep the great power locked in. The new entrants look upon Nato as a means of consolidating their freedom from Soviet power.

All these are valid short-term uses. What they do not add up to is a long-term purpose. And that, as any student of military history knows, is the only thing that can keep an alliance alive. Nato's great strength has always been that it has had a common enemy and an effective system of military command. Now it has neither. The enemy has disappeared. Most of the equipment in heavy tanks, ground forces and attack aircraft are redundant. And the command structure, as so painfully shown in Kosovo, has been undermined by differing interests in more localised situations.

That doesn't matter, argues George Robertson, the Secretary General of the organisation, because Nato now has a political purpose in reshaping the post-Cold War map of Europe to include the former Soviet republics. But if you want a political alliance, why not make a new one, or develop it around the existing institutions of the European Union? All you do by politicising the organisation is to confuse and undermine the tight central command system that has given it its success so far.

President Bush – to the deep relief of Nato staff – has instead come up this week with a new "military" purpose for the alliance, or at any rate a new enemy. That enemy is "global terrorists who hate freedom, and together we can work to defeat that enemy in the name of freedom".

It is balderdash, of course. Anyone who seriously believes that the United States is pursuing a crusade for freedom and democracy need only look to the support it has given to Uzbekistan and Pakistan since 11 September, never mind its longer-standing alliances with Saudi Arabia, China and Kuwait. What it is looking for is national security against any forces, and any countries, it perceives as threatening that security.

And why not? Alliances are made and held by self-interest not idealism, military alliances most of all. For half a century, Nato worked as one of the most successful multi-national organisations in history because the security interests of Europe and America were felt to be the same – the containment of the Soviet Union.

The trouble is that those interests have been revealed as profoundly at odds over the issue of Iraq. Washington – at least under the present Republican administration – sees its primary enemy as coming from states who are not friendly to America and have the power to launch weapons of mass destruction against it. That includes not just Iraq but Iran, North Korea and, to a lesser degree of capability, Syria and Libya. It does not, for the moment, include Pakistan, India, China, Ukraine or Israel, all of whom have access to weapons of mass destruction and threaten to destabilise their regions.

It would take a considerable exercise in casuistry to claim that this policy has anything to do with the war on terrorism as set off by 11 September. For if it did, the US has obviously much more to fear from Saudi Arabia, where terrorist cells exist throughout the country, or Yemen.

Europe, on the other hand, sees its threats as coming from precisely the other way round. On the whole it thinks that the menace from the "rogue states" is less pressing and best contained through the traditional diplomatic means of inclusion rather than isolation. The real threat is from the terrorism thrown up by poverty, instability and religious extremism in the Third World. You only have to consider the cases of Iran, Libya or North Korea to realise the huge gap that exists between the two approaches.

The particular casus belli of Iraq can be smoothed over between the allies – as it has been – through a resort to the United Nations, although it still leaves open the question of what happens if the inspectors approve the Iraqi response and Bush still decides to go to war. But the divide cannot be bridged overall. The two sides, with the presence inbetween of Tony Blair, are just too far apart. And you cannot sustain a military alliance on that basis.

Still less can you regroup that alliance, as Donald Rumsfeld, the US Defence Secretary, is insisting, around a combination of vastly increased European military expenditures and the creation of a new super rapid reaction force for what is referred to as "out-of-theatre operations".

But this only makes the basic dilemma worse. The whole debate set by US politicians about comparative defence expenditures between the US and its allies is a facile one. It is perfectly true that US military spending amounts to double that of all its Nato allies put together. But that is because the US wishes to be a global superpower keeping foreign bases in over 40 countries, maintaining permanent fleets in every ocean and a bomber capacity to reach anywhere in the world. Europe has not seen its interest in doing that since it gave up its empires.

It is true that Europe badly needs to upgrade its equipment and invest in more high-tech and carrying capacity. But it needs this quite aside from its membership of Nato. The problem of that organisation is that any decision on out-of-theatre action will only exacerbate internal tensions, not ease them.

The chief reason for opposing this desperate attempt to keep Nato on life-support, however, is that its continuation diverts attention from – actually obstructs, indeed – the development of its successors. In the end, the pattern of world defence, like the patterns of world politics, is likely to be regional. Europe, Asia and even perhaps the Arab Middle East will develop mutual support because they have to. Whether America acts as a nanny to these infants or as a broooding alternative presence has yet to be seen. But the present unipolar world leaves too great a vacuum for it not to be filled.

Behind the smiling public faces in Prague, there are few politicians and virtually no generals who will not tell you in private that they know the patient is dying. It's just that they don't quite dare to kill him off – yet.

a.hamilton@independent.co.uk