The Trakošćan Mansion was the site of the meeting at which the pair reached an agreement on a way for resolving the independence-era dispute on the border. The countries subsequently agreed to put their dispute to international arbitration.

The meeting in Trakošćan from four years ago, when both were still prime ministers, will from today be remembered with a special plaque that the pair put up as part of the celebrations.

In addition to helping to find a way of breaking the deadlock on the border dispute, the 2009 agreement also paved the way for Croatia to resume EU membership negotiations, which had come to a standstill because of Slovenian concerns over the border.

Pahor and Kosor, who is now an independent MP, stressed today that the Trakošćan meeting represented a major step towards the warming of relations between Slovenia and Croatia, which had been severely tested by the border dispute.

Also an important outcome was the building of trust between the prime ministers, which translated into greater trust between the governments and both nations.

The Trakošćan agreement allowed Croatia to join the EU this year, while the two countries had stepped up bilateral cooperation and become role models for resolving open issues in the region, the pair said.

Kosor noted that, although bringing no concrete decision, the meeting laid a foundation for a subsequent agreement on how to solve the border issue.

Pahor added that the meeting came at a time when progress seemed impossible. "Jadranka and I were condemned to our courage, reason and our responsibility to the people that we then led, but also broader to the region and the European Union."

He further said he believed that in this time that is full of bitterness and disappointment, it was right to remember moments that had brought back some optimism and faith that it is possible to overcome grave problems with courage, reason and friendship.