Lithuania became a member of the United Nations on 18 September 1991, and is a signatory to a number of its organizations and other international agreements. It is also a member of the European Union, the Council of Europe, Organization for Security and Cooperation in Europe, as well as NATO and its adjunct North Atlantic Coordinating Council. Lithuania gained membership in the World Trade Organization on 31 May 2001, and joined the OECD on 5 July 2018, while also seeking membership in other Western organizations.