The public announcement of the decision, conducted by the five-strong tribunal's president, judge Gilbert Guillaume, is reportedly attended by 25 diplomats from 17 countries, while more than 30 representatives of international media, including from Slovenia and Croatia, are also present.

Slovenia received a copy of the ruling this morning, while Croatia rejected this possibility in advance, having withdrawn from the arbitration entirely due to a 2015 scandal that was, however, not seen as a deal breaker by the tribunal.

Pressure, however, seems to be mounting on Croatia to honour its international commitments and respect the decision of the tribunal, with the German Embassy in Zagreb for instance calling on both sides today to implement the award.

The tribunal was tasked with determining the course of the 670km land border and the sea border along with Slovenia's "junction" with the high seas after the countries remained on opposite banks for almost two decades.

The agreement to turn to arbitration was also a result of Slovenia's pressure during Croatia's EU accession efforts, with one of Slovenia's main objectives being to secure undisturbed access to the high seas.

Croatia's uneasiness with the terms set to the tribunal became clear as it withdrew from the procedure in its final stage as a result of leaked recordings of phone calls between Slovenia's arbitrator Jernej Sekolec and Slovenia's agent in the case, Simona Drenik.