The prospect of Western Balkan countries one day becoming EU members is the focus of talks opening in the Bosnian capital, Sarajevo.
Of the former Yugoslav republics only Slovenia has joined the EU. Its southern neighbours are at various stages in the accession process.
The BBC Balkans correspondent says the EU will signal that more regional reconciliation is necessary first.
Both Serbia and Kosovo are represented, despite their sovereignty dispute.
Serbia has vowed never to recognise the secession of Kosovo, and to get it to the table, all state names or symbols were removed for the gathering.
Serbia has been told it must locate the remaining fugitives from the Bosnian war of the 1990s before it can join the EU. Former Bosnian Serb commander Ratko Mladic tops the list.
Macedonia's progress towards membership is blocked by Greece over its official name. Greece argues that the name should be distinct from its northern province, also called Macedonia.
Bosnia-Hercegovina and Albania are racked by political division and Kosovo's independence from Serbia still has not been recognised by five EU members.
Political commentator Tija Memisevic says integrating the Western Balkans is crucial for the EU.
"If you left things unresolved in your neighbourhood, as we saw in the 90s, it can have very negative consequences on the stability of the European Union itself," she told the BBC's Mark Lowen in Sarajevo.
"We saw it in the 90s, it can repeat again, of course not in the same way as in the 90s, but to have failed states on its borders - I don't think it's a very good idea."
The EU's foreign policy chief Baroness Ashton is attending the talks, as are representatives of the US, Russia and Turkey.