The debate on Croatia's prospective membership in the EU was organised by the Heinrich Boell foundation and the event brought together officials of Croatia, Bosnia-Herzegovina, Serbia and the EU.
Vandoren said that by playing an important role in the EU aspirations of other countries in the region, Croatia was already assisting them on that road.
The European prospect of the region is a joint interest of both the countries in the region and of Europe, the EU ambassador said, underlining the importance of regional cooperation.
The President's assistant advisor on foreign affairs, Mirjana Mladineo, said the European prospects of the countries in the region had helped efforts to bring their relations back to normal.
A representative of the German Embassy in Zagreb, Andreas Haack, said Croatia had received kudos from European partners for offering a helping hand to other countries in the region and for reiterating that it would not make the entry of its neighbours into the EU more difficult.
All of us know that another neighbour, Slovenia, has not been very helpful and that it raised a bilateral issue as an obstacle to Croatia's EU membership bid, the German diplomat said.
This behaviour is something other countries do not want to be repeated, he added.