In 1963, a large number of African and Asian countries proposed the inclusion of the subject "Question of Equitable Representation on the Security Council and the Economic and Social Council" in the agenda of the United Nations General Assembly. An agreement between African, Asian and Latin American countries made it possible to submit a reform proposal for the expansion of the Security Council which should include ten non-permanent members.
The permanent members did not approve of the reform, arguing that any expansion of the Council should be more modest.
The weight of the African-Asian bloc in the Assembly allowed for the approval of the proposed amendment to the Charter: on December 17, 1963, the General Assembly adopted Resolution 1991 (XVIII), creating four new non-permanent seats. The resolution received 97 votes in favor (Taiwan), 11 against (France and Soviet Union) and 4 abstentions (United States and United Kingdom).
The permanent members realized the high political cost of preventing the entry into force of an amendment which had been approved by the majority of Member States of the United Nations and was intended to increase the legitimacy of the Council. Thus, the five permanent members agreed to ratify the amendment in 1965.
The amendment came into force after ratification by the U.S. on August 31, 1965.