The biggest step in the formalization of the process for inviting new members came at the 1999 Washington summit when the Membership Action Plan ( MAP ) mechanism was approved as a stage for the current members to regularly review the formal applications of aspiring members . A country 's participation in MAP entails the annual presentation of reports concerning its progress on five different measures : NATO provides feedback as well as technical advice to each country and evaluates its progress on an individual basis . Once a country is agreed to meet the requirements , NATO can issue that country an invitation to begin accession talks . Currently , two countries have a Membership Action Plan : Bosnia and Herzegovina and North Macedonia . Former MAP participants were Albania and Croatia between May 2002 and April 2009 , and Montenegro between December 2009 and June 2017 , when they joined NATO . The final accession process , once invited , involves five steps leading up to the signing of the accession protocols and the acceptance and ratification of those protocols by the governments of the current NATO members
1999 Washington summit
1999 Washington summit
Enlargement of NATO