Europe's political spat over the wisdom of the Iraq war has deepened scepticism about the future of the European Union's security and defence policy. In particular, doubts have been raised about the viability of the European rapid reaction force (ERRF). But a far better target for the sceptics would be its putative Nato counterpart.

The Nato reaction force (NRF) initiative was launched at last November's Prague summit. Since then, Nato and EU officials alike have regularly asserted that the pledge to create an NRF for high-intensity warfare will not compete with the planned ERRF, which is for peacekeeping. But this is wrong. Both missions are very demanding, and European resources are scarce. Europe will have to choose - and the Nato concept is likely to lose.

At Prague, Europe agreed to reorient its forces to meet worldwide security challenges, enabling its troops to conduct demanding combat operations alongside US forces. Details about the NRF are sketchy but suggest a high - and costly - standard. Some 20,000 uniformed personnel from naval, air and ground units are to be ready at short notice to accompany US forces to distant corners of the world for 30 days at a time. To have a force this ready requires a base at least three times as large, giving a total of 60,000 people.

Nato defence planners are reluctant to offer estimates of how much the initiative will cost, perhaps because they know it will cost a lot. The average wealthy European country spends about $80,000 per soldier per year. The US spends $200,000. The British spend $155,000 dollars, and seem to produce combat units with which the US feels comfortable. To bring 60,000 troops up to the British standard could thus cost $4.5bn a year.

Pressure to find these resources will soon mount. Spurred on by Nato bureaucrats, proud European soldiers desirous of technological parity with the US will serve as a vocal lobby for the NRF. European politicians and finance ministers may demur. After all, Europeans could not agree expeditiously to send a handful of defensive assets to Turkey, a Nato ally. And Italy and Spain, great political supporters of the US stance on war, sent no forces to the Gulf. Why spend good money to create a force that Europeans will never agree to send anywhere?

While Nato officials dream of offensive punch, EU member states continue to work towards their own headline goal - the ability to deploy as many as 60,000 troops, in two months, to a demanding peacekeeping mission beyond Europe, and to sustain those forces for up to a year. Although they have earmarked the necessary numbers of soldiers, many of the supporting capabilities are still missing. Some question whether Europe would ever need to deploy so many peacekeepers.

They need not question much longer. Whether under an EU banner, a Nato banner, a United Nations banner or a national banner, European countries may soon have nearly 60,000 troops deployed - in Bosnia, Macedonia, Kosovo, Afghanistan and soon Iraq. Given the need for troop rotation in such lengthy missions, most European soldiers could be enforcing peace, preparing to enforce peace or recovering from having enforced peace for many years to come.

The NRF and the ERRF are very different animals. The EU's security and defence policy needs forces that have staying power and are politically sensitive and responsive. Their purpose is not to engage in warfare, but to discourage others from doing so. These forces need only be as speedy as the difficult diplomacy that is necessary to commit them. We know that peacekeeping and combat forces are similar but not identical because most countries that have the time to retrain regular forces for peacekeeping spend almost six months doing so.

So can European militaries build and sustain capable peacekeeping forces and highly ready combat forces at the same time without significant additional financial resources? The answer is surely "no". Yet one cannot find a senior official in either the EU or Nato who believes increases in defence spending are on the cards. Some analysts suggest that new money can be found by trimming personnel and rationalising assets. But this would be no easier politically than increasing defence budgets.

Soon Europeans and their militaries will face a difficult choice. But given Europe's already high commitment to peacekeeping, the odds are not stacked in the combat-ready NRF's favour.

Published: Financial Times, April 24 2003