World Bulletin / News Desk

Slovenia ramped up pressure on Croatia Thursday, announcing a new attempt to force its southern neighbour to respect a recent ruling that gave Ljubljana key access to the Adriatic sea.

"Slovenia can't ignore the fact that to become an (OECD) member, a state has to respect the rule of law... if Croatia or any other state does not, that could be an obstacle for it to join," Cerar told journalists.

Croatia has repeatedly said it will not implement the June ruling by an EU-backed special tribunal that drew a maritime border between the two EU member states.

Croatian Prime Minister Andrej Plenkovic pushed back against the warning, saying "blackmail leads to nowhere."

The area under dispute is a tranquil bay on the northern Adriatic Sea, where the medieval buildings of the southwestern Slovenian town of Piran tumble down to a sleepy port.

But the bay is also shared by Croatia, and the dispute over where the sea borders should be drawn has poisoned relations between the neighbours since they both declared independence from Yugoslavia in 1991.

In 2009, the two countries signed an EU-supported deal to allow the arbitration court in The Hague to solve the row over the 13 square kilometres (five square miles) of largely uninhabited land and Piran Bay.

Zagreb had only agreed to join the proceedings after Ljubljana lifted its veto in 2009 to Croatia's accession to the European Union. But it pulled out again in 2014 following a phone tapping scandal.

Ahead of high fishing season, Cerar said Slovenia will increase the presence of its police patrols in the bay to safeguard its fishermen working within the newly determined Slovenian waters covering most of the bay.

"We have to ensure the security of our fishermen. We will provide them an adequate police escort," Cerar said.