The signing of a peace agreement by the warring parties in Bosnia will be welcomed with a sigh of relief across Europe. But a peace deal is only the first step. Building and keeping the peace will require careful navigating through a mire of passionate recriminations. One of the most difficult questions is what to do with those who committed the most vicious and brutal crimes of the war.

More than 50 men have been indicted on war crimes charges by the UN tribunal in the Hague.Only one is in custody. Two of them, the Bosnian Serb leader, Radovan Karadzic, and the military commander, General Ratko Mladic, have been charged with genocide and crimes against humanity for the massacre of up to 6,000 Muslims near Srebrenica. A Bosnian Croat general,Tihomir Blaskic, has also been indicted for killing Muslims, but Croatia's President Franjo Tudjman has given him a senior position and a safe haven in Croatia.

Faced with the same problem after the Second World War, the Allies prosecuted Nazi war criminals at the Nuremberg trials, which began exactly 50 years ago today. But parallels between these events and the situation in former Yugoslavia are limited. After the Second World War, the German and Japanese regimes were overthrown and rendered incapable of further resistance. The victors could - and did - dispense their own justice.

Bosnia is different. No one side is able to dictate the terms of peace. Indeed, the pursuit of war criminals could make it harder to end the war: if those responsible for genocidal slaughter fear incarceration or worse, they may be less willing to settle the conflict.

But important principles are at stake just as they were at Nuremburg. If the new Bosnia is to survive, it must, from the start, recognise publicly the horrors that have taken place. It cannot simply turn a blind eye to the deaths of hundreds of people who were murdered in cold blood.

Malcolm Rifkind and the US peace negotiators must stick to their commitment that peace should not be made at the cost of letting war criminals go free. Whatever the nature of the accord struck, it must not include an amnesty for those guilty of the worst war crimes in Europe since the fall of Nazism.

Such a policy need not stand in the way of peace. So far, the indictment of Mr Karadzic and General Mladic has not held up proceedings in Ohio. In fact, it is unlikely that the accused will stand trial in the near future: they are safely hidden away on friendly territory. Only pressure from the major powers will convince Croatia and Serbia to hand them over.

Justice will come only slowly for those who committed war crimes. But as survivors of the Holocaust have demonstrated, the struggle to achieve it must go on. This is the least that the peacemakers owe to those who died so savagely.