"The situation is not encouraging because one must count on the negotiations not starting," he said at the end of a conference held to mark the tenth anniversary of Austria's admission to the EU.
Saying he was very sceptical about the start of Croatia's entry talks on March 17, Busek said "I believe there is no other way but to try to meet the condition (full cooperation with the Hague war crimes tribunal) from all sides and with every effort".
Busek said this was the position which some EU member countries would take and that it could not be bypassed.
The European Council decided at a summit last December that Croatia's EU entry negotiations would start on March 17 provided that it fully cooperated with the UN court.