Democracy is at risk in the Balkan countries seeking to join the European Union, with Bosnia a particular concern, Croatia's foreign minister warned.
This comes after the EU's top diplomat has promised to revive North Macedonia's membership bid.
A political crisis in Bosnia, sporadic violence between Kosovo and Serbia and political instability in Montenegro and North Macedonia - against a backdrop of a stalled EU enlargement process - risk eroding years of progress in the region.
"The situation in the Western Balkans is getting worse, divisions are deepening ... we also see the threat to democracy," Foreign Minister Gordan Grlic-Radman told reporters.
He also warned against calls for separatism in Bosnia.
"Actions echoing the 1990s need to stop," he added, referring to the ethnic conflicts of that decade following the break-up of Yugoslavia.
According to a diplomatic note seen by Reuters, EU foreign ministers meeting in Brussels were briefed on an "increasingly challenging" political situation in the Balkans.
"The public support for EU integration is receding and exclusionary nationalistic rhetoric and identity politics are gaining momentum," said the diplomatic note circulated among the EU's 27 states.
The EU's strategy to bring Serbia, Kosovo, Bosnia-Herzegovina, Montenegro, Albania and North Macedonia into the EU needs new momentum, the note said, in recognition that 18 years of efforts to bring the countries into the bloc are paralysed.
Bosnia is experiencing its gravest political crisis since the end of the war in the 1990s, reviving fears of a new conflict after Bosnian Serbs at the end of July blocked the work of the central government.
Germany threatened to cut financial support to Bosnia, labelling calls for parts of Bosnia to secede or for the Balkan state to be weakened "irresponsible and unacceptable" and naming Bosnian Serb leader Milorad Dodik as a particular culprit.
Under the US-sponsored Dayton peace accords that ended the devastating 1992-1995 war, Bosnia was split into two autonomous regions - the Serb Republic and the Federation dominated by Croats and Muslim Bosniaks, linked by a weak central government.
The country's constitution is part of the peace deal.
After North Macedonia's Prime Minister Zoran Zaev avoided a no-confidence vote last week, EU foreign policy chief Josep Borrell said on Twitter that formal EU membership talks should start soon. Bulgaria is against North Macedonia joining because of language and cultural reasons.
"Our position remains unchanged: both North Macedonia and Albania have delivered and we look forward to holding the first Intergovernmental Conferences as soon as possible," Mr Borrell said, referring to the membership talks.