The next few weeks will see the resolution, one way or another, of the last territorial issues remaining in the Balkans, where the wars of the 1990s ended with NATO interventions in Bosnia (1995) and Kosovo (1999).

Even with peace, major problems were left unresolved. Bosnia was divided between a Muslim-Croat federation and a Serb republic, with little authority vested in the central government and a large international military — and eventually civilian — presence needed to hold it together. Kosovo was left as a United Nations protectorate whose “final status” was uncertain.

These unresolved issues are now returning: Prompted by Serbia’s government, Bosnia’s Serb leadership is contemplating secession, even as its Muslim leadership tries to increase central control. And Kosovo’s Albanian population is clamoring for independence, while Serbia tries to postpone a decision by blocking action in the Security Council.

There is a real risk of renewed violence, though perhaps not on the scale of the 1990’s. Serbia wants as much independence as possible for the Serb Republic, while asserting its own sovereignty over Kosovo. Serbs governed only by Serbs on their own territory is still Serbia’s goal.

The United States and the European Union are committed to a different vision: Democratic transition and integration of all of the Balkans into NATO and eventually the EU. But they have been reluctant to impose conditions on Serbia, for fear of bringing even more radical nationalists to power. But appeasement has failed. The US and the EU must use the strong hand that they still hold to ensure that their vision prevails, bringing lasting peace to a region that has repeatedly dragged great powers into conflict.

This requires, above all, a stiff warning to Serbia that it can no longer prevent Bosnia and Kosovo from moving toward Europe. If for now a democratic Serbia prefers radical nationalism and alignment with Russia to membership in the EU and NATO, so be it. No vital US interests are at stake, and Serbia will soon recognize its mistake. The EU should be relieved not to admit such a Serbia.

At the same time, the US and the EU, acting together, must get serious in Bosnia and Kosovo. In Kosovo, now that a last-ditch round of negotiations has concluded with a report to the UN secretary-general, the US and the EU should agree to recognize Kosovo’s independence, provided the Kosovans agree to implement the plan submitted by Finnish mediator Marti Ahtisaari.

The Ahtisaari plan provides ample protection for Serbs and an international presence in Kosovo — which the US and the EU will need to deploy even without a new Security Council resolution — to ensure implementation. Ironically, Serbia’s resistance to the Ahtisaari plan undermines protection for Kosovo’s Serbs and increases the risk that they will be mistreated.

American officials are fond of pointing out that the US has repeatedly intervened to protect Muslims from war and dictatorship. But this claim will be devalued if the so far successful international interventions in Bosnia or Kosovo end in tragedy.

A satisfactory outcome in both places is within reach. To achieve it, the US and the EU must ensure that Serbia is blocked from making trouble, Kosovo becomes independent, and Bosnia stays united.