"Montenegrin succession to the NATO family of democratic nations will contribute to the stability of the region and the whole of Europe and I expect all nations to fully complete ratification in June," Stoltenberg said.
Once all member states have ratified the protocol, Montenegro will be invited to accede to the North Atlantic Treaty. It was formally invited to join the bloc in December 2015.
Russia has been concerned about NATO’s plans for Montenegro, which it regards as unwarranted expansion toward its western border. Last week, Russian Foreign Minister Sergey Lavrov said he did not see how Montenegro’s accession benefited NATO or the nation’s security.