By Jonathan Marcus Diplomatic correspondent, BBC News

Mr Medvedev is expected to win presidential elections next month

The visit of the Russian presidential front-runner Dmitry Medvedev to Belgrade is full of political symbolism.

There is an extraordinary circularity in Balkan politics. As the Austro-Hungarian Empire broke up in the wake of World War I, so countries that aspired to independence sought strong external backers to support their claims.

Nearly a century on little has changed. Once again the great powers are manoeuvring over the political fate of the Balkans.

Kosovo made sure of significant US and European support before announcing its independence a little over a week ago. And now Russia, a traditional prop of Serbian nationalism, is marking its continuing support for Belgrade.

But the question is, does Mr Medvedev's visit signal anything more? What, if anything, does Moscow plan to do to counter the Western-backed campaign for Kosovo's independence?

By any standards this is a diplomatic setback for the Russians.

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They expressed consistent and strong opposition to what they saw as the unilateral dismemberment of Serbia. They believe that the US and its allies have disregarded international law and established a precedent that could come back to haunt them.

Recognition of Kosovo is according to one Russian spokesman "an act of flagrant cynicism".

It is interesting that the Russians have tended to focus more upon Washington's role in promoting an independent Kosovo than that of the Europeans.

The worry is that this might signal that Kosovo is set to become a more significant irritant in a bilateral relationship that is already seriously under strain.

Relations between Moscow and Washington have gone seriously wrong, with the tensions increasingly apparent ever since President Vladimir Putin launched a damning rhetorical attack against America's role in the world at a Munich security conference just over a year ago.

Beyond rhetoric

The litany of disputes between Russia and the United States is significant. Russia is opposed to further Nato expansion; it does not like US plans for limited missile defences in Poland and the Czech Republic. It is uneasy about the US approach to Iran.

The diversity of its disputes with Washington suggests that Russia-US relations are not going to get better any time soon

Russia aspires to renewed influence in the wider Middle East. Above all a newly emboldened Russia flush with oil and gas revenues wants to be taken seriously on the world stage.

This is why what amounts to the dismissal of Russia's concerns over Kosovo causes such unease in Moscow.

The question remains though, beyond rhetoric, what might Russia do? The strongest response would be Russian recognition for South Ossetia or Abkhazia in their separatist struggles against Georgia.

But that might risk direct Russian involvement in a war close to its own borders; a step that Moscow may still not be ready to take. Russian spokesmen have signalled that recognition of these two territories would not be their immediate response to Kosovo's recognition by Washington.

Russia is clearly weighing up its options. It must balance its desire to maintain reasonably cordial relations with its business partners in Europe with its new assertiveness abroad.

The diversity of its disputes with Washington suggests that Russia-US relations are not going to get better any time soon; certainly not before a new president is installed in the White House in January 2009.

Russia's objective interests seem to be diverging from those of the West even as its economic linkages in the energy sector become ever more important.

In which direction will Russia choose to go; towards compromise or confrontation? How it responds to the diplomatic test of Kosovo could begin to reveal part of the answer.