Enlargement of NATO
As of 2018, NATO officially recognizes four aspiring members: Bosnia and Herzegovina, Georgia, Macedonia and Ukraine. The Federation of Bosnia and Herzegovina within Bosnia and Herzegovina has expressed willingness to join NATO, however, it faces consistent political pressure from Republika Srpska, the other political entity in the country, alongside its partners in Moscow. Macedonia has been prevented from joining the alliance by Greece, one effect of the Macedonian naming dispute. Future expansion is currently a topic of debate in several countries outside the alliance, and countries like Sweden, Finland, and Serbia have open political debate on the topic of membership, while in countries like Ukraine, support and opposition to membership is tied to ethnic and nationalist ideologies. The incorporation of countries formerly part of the Eastern Bloc and the Soviet Union has been a cause of increased tension between NATO countries and Russia.
Partnership for Peace
NATO builds relationships with partners through military-to-military cooperation on training, exercises, disaster planning and response, science and environmental issues, professionalization, policy planning, and relations with civilian government.Thirteen former member states of the PfP (namely Albania, Bulgaria, Croatia, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Montenegro, Poland, Romania, Slovakia, and Slovenia), have subsequently joined NATO. On April 26, 1995 Malta became a member of PfP; it left on October 27, 1996 in order to maintain its neutrality. On March 20, 2008 Malta decided to reactivate their PfP membership; this was accepted by NATO at the summit in Bucharest on April 3, 2008. During the NATO summit in Riga on November 29, 2006, Bosnia and Herzegovina, Montenegro, and Serbia were invited to join PfP, which they did on December 14, 2006.