(ZAGREB) - Croatian President Stipe Mesic warned Slovenia on Thursday not to block his country's European Union membership bid as such a move could seriously harm ties between the two neighbours.

"If Slovenia prevents our entry into the EU by persistently insisting on its attitudes, it will be a disaster for our future relations," Mesic said.

Such a scenario would mean that any "friendship between Slovenia and Croatia is over for good," he added.

The Croatian leader is to have an informal meeting on Friday with his Slovenian counterpart Danilo Turk, for the first time since Turk was elected in November.

Asked by journalists what he expected from the talks, scheduled to be held in Slovenia, Mesic emphasised they would be informal to give them a greater chance of success.

Croatia accuses its northern neighbour of using its current six-month term in the EU presidency to press Zagreb over unsolved bilateral issues. Slovenia has rejected the charges.

Since the two former Yugoslav republics declared independence in 1991, they have been unable to resolve a number of bilateral issues, notably their common sea-border.

The issue is linked to a disputed Croatian fishing and ecological zone.

The zone to protect fishing stocks, which was enforced by Zagreb on January 1, is strongly opposed by the European Union, and notably Croatia's Adriatic Sea neighbours Italy and Slovenia.

Brussels repeatedly warned Zagreb that imposing the zone would have negative consequences on its ambitions to join the bloc, which it hopes to do by the end of the decade.

Meanwhile, the head of the European Commission's mission here met with Mesic to discuss the current situation regarding Croatia's membership talks, which opened in 2005.

"During the past few months 'disturbing clouds have been gathering' over the talks," between Zagreb and Brussels, Vincent Degert was quoted as saying in a statement from Mesic's office.

"This could slow down the talks and in the most unfavourable situation lead to their freezing," he said.

Degert pointed to the fishing zone and more recently to relations between Ljubljana and Zagreb as the main elements which contributed to a slowdown of the talks.

Among other issues hampering the talks figures a slowness in reforming the judiciary and public administration, he added.

Mesic said he was aware of the "seriousness of the moment" adding that the unresolved border dispute with Slovenia was "at the heart of all problems."

Zagreb is ready to bring the issue before the International Court of Justice in The Hague, he added.

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