The latest round of EU-sponsored talks aimed at normalising relations between Serbia and breakaway Kosovo began Tuesday, with both parties under pressure to reach an accord.
EU foreign affairs head Catherine Ashton hosted the Serbian and Kosovo prime ministers, Ivica Dacic and Hashim Thaci, for an eighth round of talks aimed at easing tensions and paving the way for closer ties with the EU.
Ashton said Monday she believed an agreement "is within reach -- though it will not be easy," adding: "We must not let this opportunity pass."
At the previous round last month, Ashton had said "we are very close to a solution on the most difficult issues" and that Tuesday's would be a "conclusive meeting."
Washington also pressed Serbia and Kosovo to do a deal even as Serbian President Tomislav Nikolic played down hope of a breakthrough.
"We think it's important both for Kosovo and for Serbia to ... move forward both in democratic terms, in economic terms and on their path for European integration," US State Department spokeswoman Victoria Nuland said Monday.
Majority ethnic Albanian Kosovo unilaterally declared independence from Serbia in 2008, winning recognition since then from around 100 countries, including the United States and most EU member states.
Belgrade and Serbs living in Kosovo reject its independence, with the fate of some 40,000 Serbs in the north proving key to a deal.
Both sides have agreed to establish an association of Serb municipalities but Pristina refuses to grant it the executive and judicial power demanded by Belgrade.
"Intractable statements from Pristina put us before a fait accompli and are not encouraging," Serb President Nikolic said Monday.
"We must ensure the rights (for the association) are guaranteed not only by an agreement between Belgrade and Pristina, but also by the international community, primarily through the EU in its role as a mediator," he added.
Nikolic's comments come after influential Deputy Prime Minister Alexsandar Vucic, who is attending the Brussel talks, warned against any "humiliation" of his country.
Kosovo fears in turn that a large degree of autonomy for the north runs the risk the area would eventually break away.
The international community "wants to avoid at all costs the creation of a 'Serb Republic' in the north of Kosovo," said one source close to the talks, referring to the Serbian entity formed in Bosnia in 1992.
Progress at the talks is seen as essential to keeping the momentum going and Tuesday's meetings could be extended if need be, "although we do not have a lot of time," a source said.
The European Commission is due to issue a report on the negotiations on April 16 which will be forwarded to EU leaders for consideration at their end-June summit.
With a deal agreed, Serbia hopes to be given a date to start EU accession talks at a summit in June, while European Commission president Jose Manuel Barroso has said Kosovo could get an agreement on an association accord at the same time.
It might also allow the EU and NATO to wind down their military commitment to keeping the peace between the two sides who are sensitive to the least slight.