The president of the European Commission, Jean-Claude Juncker, has warned the U.S. president that calling for other EU members to leave the union could lead to war in the Balkans.

In an interview with the Financial Times, Juncker criticized President Donald Trump for encouraging other countries to copy Brexit and called this enthusiasm "annoying".

"Do not say that, do not invite others to leave, because if the European Union collapses, you will have a new war in the western Balkans," Juncker told Vice President Mike Pence when he visited Brussels earlier this year.

"If we leave them alone — Bosnia Herzegovina, Republika Srpska, Macedonia, Albania, all those countries — we will have war again."