U.S. Vice President Joe Biden is attending a summit of southeast European leaders that focuses on tensions in the region over a surge of asylum seekers and migrants crossing the territory.
Biden's trip Wednesday comes amid a debate in the United States about whether to admit Syrian refugees following the Islamic State group's attack in Paris.
Administration officials say security and humanitarian constraints are concerns for the leaders, with as many 5,000 migrants reaching Europe each day over the so-called Balkan migrant route.
The vice president will also meet with European Council President Donald Tusk to discuss the migration crisis, the fight against terrorism, the Russia-Ukraine conflict, energy and trade.
Biden will also attend bilateral meetings with Croatian and other leaders to discuss the response to the refugee crisis, energy and economic ties.