Enlargement

  • Last updated: 11 Jul. 2018 19:40

NATO’s door remains open to any European country in a position to undertake the commitments and obligations of membership, and contribute to security in the Euro-Atlantic area. Since 1949, NATO’s membership has increased from 12 to 29 countries through seven rounds of enlargement. Currently, four partner countries have declared their aspirations to NATO membership: Bosnia and Herzegovina, Georgia, the former Yugoslav Republic of Macedonia¹ and Ukraine.

Montenegro became the latest country to join the Alliance on 5 June 2017

  • NATO’s “open door policy” is based on Article 10 of its founding treaty. Any decision to invite a country to join the Alliance is taken by the North Atlantic Council on the basis of consensus among all Allies. No third country has a say in such deliberations.
  • NATO’s ongoing enlargement process poses no threat to any country. It is aimed at promoting stability and cooperation, at building a Europe whole and free, united in peace, democracy and common values.
  • Having been invited to start accession talks to join the Alliance in December 2015, Montenegro became the newest member of NATO on 5 June 2017.
  • At the Brussels Summit in July 2018, Allies welcomed the historic agreement between Athens and Skopje on the solution of the name issue and invited the government in Skopje to begin accession talks to join NATO. Full implementation of the agreement on the solution of the name issue is a condition for a successful conclusion of the accession process. Allies also urged further progress on important reforms before and after the accession process.
  • Bosnia and Herzegovina was invited to join the Membership Action Plan (MAP) in April 2010 but its participation is pending the resolution of a key issue concerning immovable defence property.
  • At the 2008 Bucharest Summit, the Allies agreed that Georgia and Ukraine will become members of NATO in future.

More background information


  • Aspirant countries

    Countries that have declared an interest in joining the Alliance are initially invited to engage in an Intensified Dialogue with NATO about their membership aspirations and related reforms.

    Aspirant countries may then be invited to participate in the MAP to prepare for potential membership and demonstrate their ability to meet the obligations and commitments of possible future membership. Participation in the MAP does not guarantee membership, but it constitutes a key preparation mechanism.

    Countries aspiring to join NATO have to demonstrate that they are in a position to further the principles of the 1949 Washington Treaty and contribute to security in the Euro-Atlantic area. They are also expected to meet certain political, economic and military criteria, which are laid out in the 1995 Study on NATO Enlargement.

  • 1995 Study on Enlargement

    In 1995, the Alliance published the results of a Study on NATO Enlargement that considered the merits of admitting new members and how they should be brought in. It concluded that the end of the Cold War provided a unique opportunity to build improved security in the entire Euro-Atlantic area and that NATO enlargement would contribute to enhanced stability and security for all. It would do so, the Study further concluded, by encouraging and supporting democratic reforms, including the establishment of civilian and democratic control over military forces; fostering patterns and habits of cooperation, consultation and consensus-building characteristic of relations among members of the Alliance; and promoting good-neighbourly relations.

    It would increase transparency in defence planning and military budgets, thereby reinforcing confidence among states, and would reinforce the overall tendency toward closer integration and cooperation in Europe. The Study also concluded that enlargement would strengthen the Alliance’s ability to contribute to European and international security and strengthen and broaden the transatlantic partnership.

    According to the Study, countries seeking NATO membership would have to be able to demonstrate that they have fulfilled certain requirements. These include:

    • a functioning democratic political system based on a market economy;
    • the fair treatment of minority populations;
    • a commitment to the peaceful resolution of conflicts;
    • the ability and willingness to make a military contribution to NATO operations; and
    • a commitment to democratic civil-military relations and institutional structures.

    Once admitted, new members would enjoy all the rights and assume all the obligations of membership. This would include acceptance at the time that they join of all the principles, policies and procedures previously adopted by Alliance members.

  • Accession process

    Once the Allies have decided to invite a country to become a member of NATO, they officially invite the country to begin accession talks with the Alliance. This is the first step in the accession process on the way to formal membership. The major steps in the process are:

    1. Accession talks with a NATO team

    These talks take place at NATO Headquarters in Brussels and bring together teams of NATO experts and representatives of the individual invitees. Their aim is to obtain formal confirmation from the invitees of their willingness and ability to meet the political, legal and military obligations and commitments of NATO membership, as laid out in the Washington Treaty and in the Study on NATO Enlargement.

    The talks take place in two sessions with each invitee. In the first session, political and defence or military issues are discussed, essentially providing the opportunity to establish that the preconditions for membership have been met. The second session is more technical and includes discussion of resources, security, and legal issues as well as the contribution of each new member country to NATO’s common budget. This is determined on a proportional basis, according to the size of their economies in relation to those of other Alliance member countries.

    Invitees are also required to implement measures to ensure the protection of NATO classified information, and prepare their security and intelligence services to work with the NATO Office of Security.

    The end product of these discussions is a timetable to be submitted by each invitee for the completion of necessary reforms, which may continue even after these countries have become NATO members.

    2. Invitees send letters of intent to NATO, along with timetables for completion of reforms

    In the second step of the accession process, each invitee country provides confirmation of its acceptance of the obligations and commitments of membership in the form of a letter of intent from each foreign minister addressed to the NATO Secretary General. Together with this letter they also formally submit their individual reform timetables.

    3. Accession protocols are signed by NATO countries

    NATO then prepares Accession Protocols to the Washington Treaty for each invitee. These protocols are in effect amendments or additions to the Treaty, which once signed and ratified by Allies, become an integral part of the Treaty itself and permit the invited countries to become parties to the Treaty.

    4. Accession protocols are ratified by NATO countries

    The governments of NATO member states ratify the protocols, according to their national requirements and procedures. The ratification procedure varies from country to country. For example, the United States requires a two-thirds majority to pass the required legislation in the Senate. Elsewhere, for example in the United Kingdom, no formal parliamentary vote is required.

    5. The Secretary General invites the potential new members to accede to the North Atlantic Treaty

    Once all NATO member countries notify the Government of the United States of America, the depository of the Washington Treaty, of their acceptance of the protocols to the North Atlantic Treaty on the accession of the potential new members, the Secretary General invites the new countries to accede to the Treaty.

    6. Invitees accede to the North Atlantic Treaty in accordance with their national procedures</