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.
Enlargement of NATO
Christopher Sands of the Hudson Institute proposed Mexican membership of NATO in order to enhance NATO cooperation with Mexico and develop a "North American pillar" for regional security. In June 2013, Colombian President Juan Manuel Santos stated his hope that Colombia's cooperation with NATO could result in NATO membership, though his Foreign Minister, Juan Carlos Pinzon, quickly clarified that Colombia is not actively seeking NATO membership. Ivo Daalder and James Goldgeier proposed a "global NATO" that would incorporate democratic states from around the world, including Australia, New Zealand, Japan, South Korea, Brazil, South Africa, and India, while Republican presidential candidate Rudy Giuliani suggested expanding NATO to include Singapore, Israel, Australia, India, and Japan. Expanding NATO outside of Europe would require amending Article 10 of the North Atlantic Treaty.