A troika of envoys from the US, EU and Russia have met Serbian leaders for talks on finding a solution to the long-term political status of Kosovo.
The troika of envoys said they would not make new proposals on Kosovo
The US envoy, Frank Wisner, said "every possible option" for a compromise solution would be explored.
They will travel next to Kosovo for talks with ethnic Albanian leaders.
The UN Security Council failed last month to find consensus on the Serbian province's future. Its majority ethnic Albanian population wants independence.
Mr Wisner said he and his troika colleagues will "leave no stone unturned" in their search for "a successful outcome, peace in the region and a better future for Serbia and Kosovo".
The envoys met Serbia's President Boris Tadic and Prime Minister Vojislav Kostunica, who have rejected independence for Kosovo.
The mostly-ethnic Albanian Kosovo has been under UN administration since a war in 1998-99 between ethnic Albanian separatists and Serb forces.
Ethnic Albanians want Kosovo to become independent. Serbs want the province to remain a part of Serbia.
A UN proposal to provide a form of supervised independence was blocked at the UN Security Council last month by Russia, which is a close ally of Serbia.
The current round of talks are due to end in December, but Serbia and Russia have said there should be no time limit.
"We are going to support the Kosovo status process in order to help reach a compromise solution which can be endorsed by the UN Security Council," said the Russian envoy Alexander Botsan-Kharchenko.
The EU representative of the troika, the German diplomat Wolfgang Ischinger said the talks had been a "first business meeting" for the troika.
He said on Thursday that the troika would not be making any new proposals but would be seeing whether the Serbian and Kosovo-Albanian sides had any chance of finding agreement over the long-term status of Kosovo.
International officials in Kosovo have expressed concern that if the issue is not resolved in the near future, the security situation in the province could deteriorate.
Many believe the talks chaired by the troika could be the last opportunity to find an agreement between the two sides, says the BBC's Nick Hawton in Sarajevo.