Also planned to be on the agenda of the informal talks is EU enlargement and the crisis in Ukraine.

Pahor's office announced that the Brdo process of cooperation among the Western Balkans and the EU will also be raised.

The presidents are scheduled to speak to the press at 1:15 PM and close their meeting by touring a selection of cultural institutions in the Austrian capital.

The meeting of the heads of state from the three countries is part of an effort to boost trilateral cooperation and coordination on EU issues, initiated by Austria and Slovenia after Croatia joined the EU in July 2013.

The initiative was opened with a meeting of the heads of government, Austrian Chancellor Werner Faymann, Croatian PM Zoran Milanović and Slovenian PM Alenka Bratušek in Graz in August.

Pahor will be visiting Vienna only days after Austrian Foreign Minister Sebastian Kurz paid a visit to Ljubljana.