Côte d'Ivoire was admitted to UN membership on 20 September 1960 and is a member of ECA and all the nonregional specialized agencies, as well as the WTO. It belongs to the African Union and various other intergovernmental organizations, including the African Development Bank and G-77. Together with other countries of former French West Africa, it participates in the West African Customs Union, and it was the organizer of the Conseil d'Entente, which unites Benin, Niger, Togo, and Burkina Faso in a customs union. In May 1975, Côte d'Ivoire was one of the signatories to a treaty that created ECOWAS, an economic organization that includes both French-and English-speaking West African countries. Abidjan is the headquarters for the African Development Bank (although as of 2003 operations of the bank were temporarily relocated to Tunis, Tunisia), and houses the secretariat of the Conseil d'Entente and the West African office of the World Bank.