Falling short of telling Croatia to respect international law and implement the arbitration decision, he offered Austria's assistance.

"We'll do everything to solve this problem," the Austrian Press Agency (APA) quoted Van der Bellen as saying after the meeting with Slovenia's Borut Pahor and Croatia's Kolinda Grabar-Kitarović.

Austria has a "typically Austrian neutral position" with respect to the June ruling of the international arbitration tribunal, Van der Bellen reportedly told the press, adding that good relations with both countries meant a lot to him.

He nonetheless repeated the Austrian stance that Slovenia and Croatia should see the arbitration ruling as the "decisive step to a final settling of the dispute".

Pahor and Grabar-Kitarović meanwhile repeated their countries' respective positions, with Pahor stressing that the question is not if the arbitration decision will be implemented but "when and how".

The decision is internationally binding and Slovenia is "waiting for a small signal from the Croatian side that it is ready to implement it".

The trilateral meeting, the fourth of this kind since 2014, meanwhile focused on the future of Europe and the Western Balkans, with the trio noting they had similar views.

"The prospect needs to be kept open for these countries to sooner or later become EU members," the Austrian host said.

Pahor argued that the pace of enlargement needed to reflect the effectiveness of the reform process in Western Balkan countries, while stressing that enlargement needed to be a political and not a technical, administrative process.

Grabar-Kitarović said that Croatia would push above all for the membership of Bosnia-Herzegovina, both in the EU and NATO, arguing Bosnia's stability was important for the entire region.

The Austrian and Slovenian presidents moreover offered help to Croatia in its battle with the wildfires raging in the Split area.

The presidents agreed to continue their debates on regional cooperation in what has become a traditional trilateral format. Slovenia will be the host country next year, Pahor's office announced.