Rehn made the statement during a visit to Ljubljana, where he held talks with Foreign Minister Dimitrij Rupel, Prime Minister Janez Jansa and President Janez Drnovsek.
The border issue is a bilateral issue dealt with by the countries concerned, Rehn told reporters commenting on proposals in Slovenia that the EC act as a mediator between Zagreb and Ljubljana in the settlement of border issues in the course of Croatia's talks on membership of the EU.
If the bilateral issue of borders is separated from the issue of the fishing regime, the EC will be ready to help find a pragmatic solution to the fishing regime to prevent further incidents in the border area, Rehn said.
The area in question stretches from Vrsar in Istria, Croatia, to Ankaran on the Slovene Adriatic coast, Rehn added.
Slovenia's position is that the border problem should be solved in bilateral talks, Minister Rupel said.