Brussels - A row over border demarcation which has led European Union member Slovenia to block its neighbour Croatia's EU hopes is set to move up a level on Monday as EU foreign ministers debate the issue for the first time.

Diplomats in Brussels fear that the Slovenian block, which comes as the accession negotiations of Turkey and Macedonia are also stalled because of rows with individual EU members, is casting a shadow over the EU's entire enlargement policy.

"There is a growing issue of the credibility of the enlargement process," said one EU diplomat who asked not to be named.

The row over where the sea border between the former-Yugoslav states should lie has been a sore point since 1991, but it jumped up the political agenda in December when Slovenia refused to let Croatia move any closer to the bloc until it was solved.

The European Commission, the EU's executive, which oversees the accession process, has since brokered several rounds of talks between the two countries in a bid to lift Slovenia's veto.

Most recently, EU Enlargement Commissioner Olli Rehn on Wednesday proposed a compromise aimed at unfreezing the negotiations without having to submit to the arbitration of the International Court of Justice - a process which could take years.

Croatia welcomed the proposal, but on Thursday Slovenia cancelled talks between the two countries' prime ministers on the issue.

The EU responded by postponing for the second time a set of accession talks with Croatia planned for Friday.

"We cancelled it because there is no chance to close or open further (negotiating) chapters," EU presidency spokesman Jan Sliva told the German Press Agency dpa. (dpa)