The two-day conference is focusing on the U.N.-mediated negotiations on the future of Serbia's breakaway province of Kosovo. Officials will also discuss the broader region's economic development and drive to join the EU.
In opening remarks, Socialist leaders voiced strong support for the integration of the Western Balkans into the European Union, the AP reports.
The head of the Party of European Socialists, Poul Nyrup Rasmussen, called the conference "a new start for bringing the EU and the Western Balkans closer together."
Serbian President Boris Tadic expressed optimism about his country's hopes of joining the EU. He added, however, that this requires support from the 25-nation bloc.
The host of the meeting, Bulgarian Prime Minister Sergei Stanishev, said that for the Socialists it was very important that the integration process continues after the accession of Bulgaria and Romania, the AP reports.
Stanishev also stressed the importance of the future status of Kosovo, which will be "decisive for the stability of the whole region and its European perspective."
Montenegrin President Filip Vujanovic said that the future of Kosovo should be decided by a dialogue between Belgrade and Pristina with the participation of the international community. Montenegrin voters last week chose independence from Serbia.