The leaders of Slovenia and Croatia, locked in a border dispute that has blocked Zagreb's European Union membership bid, spoke on the phone for the first time on Wednesday and agreed to meet this month.

"Prime Minister Ivo Sanader has rung Slovenian Premier Borut Pahor... They discussed bilateral relations and agreed to meet soon," said a Croatian government statement, signalling a possible new chapter in the 18-year-old row that has frustrated the EU.

Slovenia, which joined the EU in 2004, vetoed in December the opening and conclusion of a number of areas in neighbouring Croatia's EU entry talks because of the border row.

Diplomats say that unless the dispute is resolved quickly, Croatia may fail in its goal of completing entry talks this year and joining the 27-nation bloc in 2011, although Sanader repeated this week Croatia still aimed to wrap up the talks as planned.

Details and the exact date of the prime ministers' meeting would be agreed later, the Croatian statement said.

It was their first contact since Pahor came to power last September. The Slovenian struck a cautious note on Wednesday, saying the meeting would be "informative".

"We have called it an informative meeting, because we do not wish the public to expect the problem will be solved at the meeting," Pahor said.

Local media said both Sanader and Pahor would separately meet French President Nicolas Sarkozy this month. In December, France pushed for, but failed to get, a diplomatic solution to the row while it held the EU's rotating presidency.

Slovenia blocked Zagreb in the EU talks, saying documents Croatia was using in negotiations were prejudicial to the border dispute. Zagreb said it was ready to make a formal statement this was not the case.

The European Commission, keen to see enlargement on track, has asked Nobel Peace Prize winner Martti Ahtisaari, former Finnish president and veteran diplomat, to help mediate in the conflict if both parties agree to it.

Experts from both countries said last week they had identified six km (4 miles) of disputed land border. There was less progress on the sea border in the northern Adriatic, where Slovenia, squeezed between Italy and Croatia, seeks full access to international waters.