The next likely candidate for EU membership, after Romania and Bulgaria, is Croatia "which will be ready (for membership) faster than other western Balkan countries", Rehn said. "Croatia could join the EU if the Union adopts a new institutional framework by the end of the decade."
"The EU must reach agreement on its institutional framework in the near future. There is one proposal for that, a constitutional agreement, which I personally support. The Nice agreement guarantees the institutional framework of a 27-member EU, including Bulgaria an Romania," Rehn said.
Asked if Montenegro, which voted for independence at a referendum last Sunday, had a European prospect, Rehn said that Montenegro, Serbia and all other western Balkan countries had a concrete medium-term prospect of membership if they met the set criteria.
"However, those two countries face different challenges. Montenegro must first improve its administrative capacity in many areas. Serbia can continue negotiations with the EU as soon as it starts full cooperation with the Hague war crimes tribunal," the EU official said.