Member states of NATO members and three former Yugoslav republics) from 12 March 1999 to 5 June 2017. NATO has added new members seven times since its founding in 1949, and since 2017 NATO has had 29 members. Twelve countries were part of the founding of NATO: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom, and the United States. In 1952, Greece and Turkey became members of the Alliance, joined later by West Germany (in 1955) and Spain (in 1982). In 1990, with the reunification of Germany, NATO grew to include the former country of East Germany. Between
Enlargement of NATO by nationalist Prime Minister Vladimír Mečiar. Romania and Slovenia were both considered for invitation in 1997, and each had the backing of a prominent NATO member, France and Italy respectively, but support for enlargement was not unanimous, particularly in the US Congress. In an open letter to US President Bill Clinton, more than forty foreign policy experts including Bill Bradley, Sam Nunn, Gary Hart, Paul Nitze, and Robert McNamara expressed their concerns about NATO expansion as both expensive and unnecessary given the lack of an external threat from Russia at that time. A 2006 study in the journal "Security Studies"