The breakdown of talks between Serbia and Kosovo, well before next week's deadline for an agreement, threatens a period of new and dangerous instability, not only between these two entities, but across the region. There now seems little to hold back Kosovo's newly elected government from declaring independence; nothing, either, to dissuade Russia from exercising its veto in the UN Security Council on behalf of its fellow Slav country, Serbia.
So far, the authorities in both Serbia and Kosovo say they will not resort to violence. The best intentions of governments, however, have a way of being overtaken by local passions. Kosovans will be frustrated if their quest for statehood is thwarted. Unemployment is high; there is a young population. The smallest spark could ignite a conflagration.
The EU has called for restraint on both sides not least out of self-interest, because it is divided about how to proceed. Pragmatists understand the perils of disappointing Kosovo and see independence as inevitable. Constitutionalists fear the consequences of a Kosovan state that lacks Serbia's acceptance. They also see a disconcerting precedent.
If Kosovo, which is far from being able to stand on its own economic feet, becomes nominally independent, what about Republika Srpska in Bosnia? What about the "frozen" conflicts left by the Soviet collapse: the ethnic Russian enclaves in Georgia and Moldova, the Armenians of Nagorno-Karabakh? What price peace in south-east Europe and the Caucasus, were they to follow suit? And what might be the implications for the Spanish enclaves in North Africa, and the colonial borders elsewhere in that continent?
The constitutionalists are not wrong to see destabilising parallels. But the greater and more immediate risk would be to deny Kosovo independence. The EU is right to call for further talks, and right to ask Kosovo's new government to think twice before making any unilateral move. But it will not be able to restrain the ambitions of its ethnic Albanians for long.
The hope had been that Serbia and Kosovo would be able to divorce by mutual consent, rather as Czechoslovakia split, if rather less harmoniously. Recent history, demography and the location of sacred Orthodox sites made that prospect unlikely.
The EU must now look to what can be salvaged. It must accept that Kosovo will declare its independence; that Serbia along with many African states will refuse recognition; and that Russia will use its UN veto. An uneasy state of semi-recognition may be the best that can be expected, with formal recognition in time following the facts on the ground. Such a peaceful and gradualist outcome, however, will depends on all parties showing restraint.