An international envoy says the partition of Kosovo could be acceptable as a way of breaking the deadlock over the province's future.
Wolfgang Ischinger said all options would be considered
The division of the Serbian province has previously been taboo.
But a troika of envoys holding top-level talks on the issue have so far failed to find any compromise acceptable to both Serbia and Kosovo.
EU envoy Wolfgang Ischinger said partition could be an option if both sides agreed.
"It is the principle of the troika to be prepared to endorse any agreement which both parties manage to achieve. That includes all options," Mr Ischinger said.
Asked if that included splitting the territory in two, he replied: "If they want that."
The troika of envoys from the US, EU and Russia have held talks in the Serbian capital Belgrade, and are now meeting leaders in Kosovo to try to break the impasse over the province's future.
They have described their negotiations as the last chance to reach a deal.
The leaders of Kosovo's majority ethnic-Albanian population have said only independence will do.
Serbia has rejected that outright.
Western nations have proposed a form of conditional independence, but Russia has refused to let that past the UN Security Council unless Belgrade agrees.
The division of the province - presumably with a northern slice, where many of Kosovo's 10% Serb population live, remaining as part of Serbia - is seen as a possible way of breaking the stalemate, even though virtually all parties have previously rejected it.
"We are urging both sides to think outside the box," said Mr Ischinger.
"If both sides repeat their classic positions, there is little hope for compromise or bridge-building."
Partition of Kosovo along the line of the Ibar River has long been proposed by influential circles in Belgrade, but it is opposed by Albanian leaders and also by many Serbs who live in enclaves to the south of the river, says the BBC's Eastern Europe correspondent Nick Thorpe.
Most of the historic Serbian religious sites, including famous churches and monasteries like Gracanica, Pec, Prizren and Decan would remain in the Albanian part.
The loss of the main town - northern Mitrovica - to Serbia would also deprive the remaining Serbs of much of their negotiating weight within the Kosovo Assembly.
It could also raise fears of partition elsewhere in the Balkans - in the Presovo Valley in southern Serbia, and in Bosnia.
However, the envoys are under pressure to come up with some sort of solution.
There are concerns that the increasingly frustrated ethnic Albanian leaders will unilaterally declare independence if a deal is not reached.