The European Union's enlargement commissioner says that Serbia must reach an agreement on normalization of relations with Kosovo if it wants to join the bloc.

Johannes Hahn said after meeting Serbia's president, Aleksandar Vucic, on Wednesday that the EU won't import any unresolved disputes with future new member states.

Hahn visited Belgrade a day after the European Commission released a new strategy paper for the western Balkans region that envisages Serbia could join the bloc in 2025 if it meets all necessary conditions and carries out reforms. The commission said the six Western Balkan EU hopefuls must resolve all disputes in order to be invited in.

Serbia has refused to recognize Kosovo's 2008 declaration of independence. Vucic said that any future agreement should be the result of a "compromise."