Front row (R-L) Croatian President Kolinda Grabar-Kitarovic, U.S. Vice-President Joe Biden, European Council President Donald Tusk, Slovenian President Borut Pahor, and top row Albanian President Bujar Nishani (L), Serbian President Tomislav Nikolic (L2), Macedonian President Gjorge Ivanov (L3), Montenegro President Filip Vujanovic (L4), Austrian President Heinz Fischer (L5), Kosovo President Atifete Jahjaga (L6) BiH Presidency Chairman Dragan Covic (L7), BiH Presidency Member Bakir Izetbegovic (L8) and BiH Presidency Member Mladen Ivanic (R) pose for a family photo of Brdo-Brijuni Process summit, gathering heads of state from countries in the area of the former Yugoslavia plus Albania in Zagreb November 25 2015 (Photo: AFP)
US Vice President Joe Biden arrived in Zagreb on Wednesday for a Western Balkans summit, highlighting renewed interest from Washington in the fragile region as it deals with an unprecedented influx of refugees.
A 4,000-strong police deployment lined the Croatian capital and some schools were closed downtown ahead of the afternoon summit, which brings together eight heads of state and European Union president Donald Tusk.
Few details of the agenda have been released, but the migrant crisis and concerns over global terror threats after this month's deadly Paris attacks were expected to loom large over the talks.
Biden told reporters in Zagreb that the United States has "had an overwhelming interest in this region for the last 25 years". He was due to make a longer statement later on Wednesday.
Ahead of the summit Biden met various leaders including Slovenian President Borut Pahor, who said they had discussed how to reduce the number of migrants and preserve stability in the region, without giving details.
Pahor, who is co-hosting the event, earlier said that the summit aimed to boost "cooperation and mutual trust at a moment of increased security risks".
Along with European Union members Slovenia and Croatia, the Brdo-Brijuni Summit brings together the presidents of Albania, Bosnia, Kosovo, Macedonia, Montenegro and Serbia, all of which aspire to join the EU.
"The US is arriving in a bid to avoid destabilisation of the region, notably in the light of new threats," said Lidija Cehulic-Vukadinovic, international relations professor at Zagreb University.
"The Balkans remains a potential powder keg," she told AFP.
The region is burdened by the legacy of the 1990s wars that accompanied the break-up of the former Yugoslavia, and it was a US-brokered peace deal 20 years ago that ended the bloodiest conflict in Bosnia.
The Western Balkans still face numerous challenges, from high youth unemployment and slow economic reforms to fragile inter-ethnic relations and threats from a small number of homegrown Islamic extremists, particularly in Bosnia.
Analysts said Biden's visit signalled a return of Washington's interest in the region, having shifted its focus since the 1990s to the Middle East and ceded watch over the Balkans to the European Union.
"The US is back at the table. Europe has failed to resolve many issues" in the Western Balkans, Cehulic-Vukadinovic said.
In recent months, hundreds of thousands of migrants and refugees fleeing war and poverty in the Middle East, Asia and Africa have travelled from Greece along the so-called Balkans route to northern Europe.
The crisis has at times strained relations between Western Balkan neighbours and former foes as they grapple with how best to manage the huge influx.
Countries on the route said last week that they were restricting the crossings of economic migrants and allowing in only people from war-torn countries such as Syria, Iraq and Afghanistan, sparking protests from others stuck at the Greek-Macedonian border.
The United Nations has warned that the tightening of restrictions is creating an increasingly untenable situation, stranding many outdoors as temperatures plunge.