External differentiation as a strategy of system maintenance: EU enlargement towards the Western Balkans

Despite the stalling of enlargement countries’ accession to the EU, these coun-tries have been recurrently involved in EU policies. There is, however, littleknowledge about their participation in EU policies short of membership. Thisarticle conceptualises such participation as a manifestation of external differen-tiated cooperation. It offers a theoretical approach accounting for the unfold-ing of external differentiated cooperation in EU interactions with enlargementcountries as a strategy of system maintenance. External differentiated cooper-ation, the article argues, serves as a strategy for the EU to address increasedmutual dependences with enlargement countries triggered by crises-inducedshocks to the EU system of regional integration. By examining EU-WesternBalkans’ interactions from 2014 to 2023, the article shows that the EU and itsrelevant actors have resorted to external differentiated cooperation to ensurethe functioning of the EU system of regional integration against the backdropof member states’ reluctance towards EU enlargement.