MOSCOW (Reuters) - Russia acknowledged on Thursday that getting Serbs and Albanians to compromise on Kosovo in upcoming talks would be "unbelievably difficult."

The comment came in an interview with Russian diplomat Alexander Botsan-Kharchenko, Moscow's man in a troika of diplomats making a last-ditch bid to break the deadlock over Serbia's breakaway province.

The assessment is in line with Western warnings that bridging the gap between Albanian demands for independence and Serbia's total rejection of it could be impossible.

But Botsan-Kharchenko insisted that the new talks, which get under way in Vienna next week and which Moscow forced on the West, be open-ended and not subject to a December 10 deadline favored by the United States, the European Union and the United Nations.

Kosovo has been run by the U.N. and protected by a NATO peace force since 1999, when the West bombed Serbia to compel the withdrawal of its forces during a counter-insurgency war. The troika was set up last month after Russia, Serbia's main ally, repeatedly blocked Western drafts of a U.N. resolution based on a plan by United Nations envoy Martti Ahtisaari to give Kosovo independence under EU supervision.

"The troika itself will not offer any solutions - we are waiting for the sides to find them," he said. As for making a report to U.N. Secretary General Ban Ki-moon by Dec .10, that should not be seen as an end to the mediation bid.

Washington has said it is prepared to recognise Kosovo even if independence is not endorsed by the United Nations. Most of the 27 EU member states agree, viewing self-determination for the 90 percent Albanian majority as the only viable solution. Russia warns that recognizing Kosovo's independence without Belgrade's agreement is a violation of sovereignty and U.N. principles which could embolden separatist movements across Europe from the Balkans to the Caucasus region.