The Serbs have a word for it. Inat. It is defined in my dictionary as spite, malice or grudge, but that doesn't really do it justice. The scholar Dragan Milovic called it "proud defiance, stubbornness and self-preservation – sometimes to the detriment of everyone else or even oneself".

I suspect that, despite the temporary warm glow and relief in the chanceries of Europe from the narrow win by the pro-Western Boris Tadic over his ultra-nationalist Radical candidate Tomislav Nikolic (whose party leader is the absentee, in The Hague, warlord Vojislav Seselj), we shall see much evidence of inat in the weeks to come.

A win for the nationalist Nikolic would have been seen as an egregious example of it, a dangerous turn by the Serbs away from Europe and the West and a return to the nationalism of the 1990s, bolstered by the support of a resurgent Russia.

Yet in truth it is too early for the foreign ministries of Europe and the US to celebrate. The big issue of Kosovo, with its capacity to destabilise the region, has not gone away, and those ministries have consistently misread the Serbs over Kosovo. They believe that offering the prospect of eventual EU membership would sufficiently sweeten the pill of soon-to-be-declared Kosovo independence (while it will be widely recognised in the West, it won't extend to the UN where a Russian veto will prevent a Kosovo seat being created) as to reconcile Serbs to giving up Kosovo.

But although Tadic has won, his freedom to manoeuvre on Kosovo is severely limited. The president is effectively less powerful than the prime minister, and no politician in Serbia can afford to shrug off the loss of Kosovo. The democratic nationalist prime minister, Vojislav Kostunica, refused to support either candidate in the second round run-off, despite being in coalition in parliament with Tadic's Democratic Party, a coalition committed to a robust but so far unannounced package of measures to be implemented if Kosovo declares independence.

As to what they are, one can only speculate, but they seem likely to involve suspension or downgrading of diplomatic relations with those countries like the UK which recognise Kosovo, a trade embargo on Kosovo itself, other than the largely Serb area north of the Ibar river adjacent to Serbia proper, and the setting up of parallel institutions and a physical presence in what will become a Serb statelet in Kosovo. In other words, a form of de facto partition.

The West will claim that this is illegal and against the UN Security Council Resolution of 1999 setting up a UN administration in Kosovo as part of Serbia. The Serbs will respond that recognition of an independent Kosovo without a new Security Council Resolution is itself illegal and a partition of Serbia itself.

Will the region erupt into violence again? Probably not. But one spark in the Balkans has proved sufficient to ignite a conflagration in the past, and as recently as March 2004, events on the ground in Kosovo looked capable of overwhelming the 18,000 international forces there when several Serbs were killed and dozens of Serbian houses and churches were destroyed.

The pro-Western forces in Serbia will be severely weakened by any perceived loss of Kosovo, and the tensions between Kostunica and Tadic in handling the confrontation with the West may stretch to breaking point. In the event of the collapse of the present governing coalition, the Radicals, despite their loss of the presidential elections, would almost certainly reinforce their present position as the largest single party at subsequent parliamentary elections and would use their mandate, in coalition with Milosevic's Socialist Party, to step up the level of confrontation with the West.

The West needs to provide some serious gains for the pro-Western parties. Re-thinking their opposition to the partition of Kosovo might be a useful start. Opening up a European perspective for Serbia in the near, rather than distant, future would be another.

As it was, only last week, because the butcher of Srebrenica, Ratko Mladic, is perceived to be hiding in Serbia, the EU refused to sign a Stabilisation and Association Agreement, the first step on the path to EU membership, with Serbia.

At the moment the pro-Westerners in Belgrade have too little to show for following the path of western liberalism since the fall of Milosevic seven years ago. Inat, the Serbian cult of cutting off one's nose to spite one's face, may well lead to a prolonged period of confrontation. And Russia, which has just signed an energy agreement with Serbia, will relish having a dependent ally in a strategically vital position in a still disturbed region.

The author is president of Trinity College, Oxford, and a former ambassador to Yugoslavia