Does the United Nations need its own army?

Should the United Nations have an army? The 8,000-strong peace-keeping force in blue berets in Sierra Leone is not powerful enough to take on and defeat the rebel forces should they decide to resume full-scale civil war. Its role is to police last year's peace agreement between the democratically elected government and the rebels. Seven peace-keepers have been killed, however, and now 50 have been taken prisoner, as they are dragged into increasingly direct military confrontation with the bandit army of Foday Sankoh.

The danger is that the UN will find itself in a Bosnian situation - at best observing; at worst caught up in a civil war.

So, should the UN engage more forcefully in this desperately poor African country to protect its people from the rebels who are living off the diamonds that are Sierra Leone's main natural resource? Of course it should, if it can, but the issue is hardly straightforward. The usual model would be for the UN to approve intervention by a concerned regional power. That is, indeed, how the rebels were ousted and the legitimate government of Ahmed Tejan Kabbah restored two years ago - by Nigerian forces assisted by British mercenaries. Not only did that cause a little domestic difficulty for the Foreign Secretary, Robin Cook, who said he did not know what his subordinates were up to, but it meant relying on the Nigerian military dictatorship, which has many previous convictions for human-rights abuses.

But if the Nigerians cannot do it, who can? After the United States's ill-fated attempt to intervene in Somalia in the early 1990s, direct involvement by Western forces under a UN mandate seems unwise. The alternative would be for the UN to have greater military forces supplied by member countries but under UN command and able to engage in peace-making rather than just peace-keeping. But despite brave talk, after the Kosovo war, of Britain and other Western nations providing units for a UN rapid-deployment force, it is hard to see how a credible multinational force can be anything other than several years away.

The way forward in Sierra Leone, therefore, is bound to be one of messy compromises, both with the rebel leaders and with Nigeria. The UN is right to increase the peace-keeping force to 11,000 troops, but they cannot be expected to fight the Sierra Leoneans' civil war for them. Tony Blair and Mr Cook need to be more explicit about why Britain cannot always do "what it takes", which is what Mr Blair promised in Kosovo, to right every injustice in the world.