Eight European Union countries will meet in Brussels Sunday to discuss Europe’s largest migration crisis since World War II, a development that could affect the increasingly heated political disagreements among EU nations over the controversial issue.

European Commission President Jean-Claude Juncker called the meeting, which is expected to be attended by Austria, Bulgaria, Italy, France, Germany, Greece, Malta and Spain.

The leaders will explore how to stop migrants from relocating to different EU countries after claiming asylum in one of the Mediterranean countries they initially entered.

The meeting will precede an EU summit later this month at which leaders will attempt to finalize a joint migration policy three years after more than 1 million people entered Europe, primarily those fleeing violence in the Middle East and Asia.

The issue has threatened German Chancellor Angela Merkel’s domestic coalition and triggered a firestorm over a boatload of migrants who were rescued from the Mediterranean Sea but were subsequently turned away by Italy’s new right-wing government.

On Monday, Germany’s conservative Christian Social Union gave Merkel two weeks to secure a European agreement. CSU leader and Interior Minister Horst Seehofer wants Germany to turn away migrants who have already registered in other EU countries. Merkel, however, opposes any unilateral moves that would undermine her 2015 open-door policy and her authority.