"Today, the European Union signed an agreement with Montenegro on border management cooperation between Montenegro and the European Border and Coast Guard Agency (Frontex).(...)"
See: Council of the European Union: Border management: EU signs agreement with Montenegro on European Border and Coast Guard cooperation (link);
“The objective of this agreement is to allow Frontex to coordinate operational cooperation between EU Member states and Montenegro on the management of the borders that the European Union and Montenegro have in common. The signing of this agreement is yet another demonstration of the deepening and expanding cooperation with Montenegro. It will bring benefits for both parties, in particular in enhancing border management activities.”
See: Full-text of agreement (pdf)