Igor Lukšić

"Montenegro has achieved progress in pursuing reforms and standards within the integration processes, particularly in the field of security, rule of law and strengthening of the public support for NATO integration," Biden said on Tuesday after meeting Montenegro's Prime Minister, Milo Djukanovic.

Montenegro's Deputy Prime Minister and Foreign Minister, Igor Luksic, said Montenegro had no option but to join NATO, if only for reasons of cost.

Maintaining military neutrality would involve building a defence system that would be more expensive for Montenegro than joining NATO, he said on Thursday.