The United Nations Security Council "veto power" refers to the power of the permanent members of the UN Security Council (China, France, Russia, United Kingdom, and United States) to veto any "substantive" resolution. A permanent member's abstention or absence does not prevent a draft resolution from being adopted. This veto power does not apply to "procedural" votes, as determined by the permanent members themselves. A permanent member can also block the selection of a Secretary-General, although a formal veto is unnecessary since the vote is taken behind closed doors.
The unconditional veto possessed by the five governments has been seen by critics as the most undemocratic character of the UN. Critics also claim that veto power is the main cause for international inaction on war crimes and crimes against humanity. However, the United States refused to join the United Nations in 1945 unless it was given a veto. The absence of the United States from the League of Nations contributed to its ineffectiveness. Supporters of the veto power regard it as a promoter of international stability, a check against military interventions, and a critical safeguard against U.S. domination.
Article 27 of the United Nations Charter states:
Although the "power of veto" is not explicitly mentioned in the UN Charter, the fact that "substantive" decisions by the UNSC require "the concurring votes of the permanent members", means that any of those permanent members can prevent the adoption, by the Council, of any draft resolutions on "substantive" matters. For this reason, the "power of veto" is also referred to as the principle of "great power unanimity" and the veto itself is sometimes referred to as the "great power veto".
The idea of states having a veto over the actions of international organizations was not new in 1945. From the foundation of the League of Nations in 1920, each member of the League Council, whether permanent or non-permanent, had a veto on any non-procedural issue. From 1920 there were 4 permanent and 4 non-permanent members, but by 1936 the number of non-permanent members had increased to 11. Thus there were in effect 15 vetoes. This was one of several defects of the League that made action on many issues impossible.
The UN Charter provision for unanimity among the Permanent Members of the Security Council (the veto) was the result of extensive discussion, including at Dumbarton Oaks (August–October 1944) and Yalta (February 1945). The evidence is that the UK, US, USSR, and France all favoured the principle of unanimity, and that they were motivated in this not only by a belief in the desirability of the major powers acting together, but also by a concern to protect their own sovereign rights and national interest. Truman, who became President of the US in April 1945, went so far as to write in his memoirs: "All our experts, civil and military, favored it, and without such a veto no arrangement would have passed the Senate."
The veto was forced on all other governments by the (soon to be) five veto holders. In the negotiations building up to the creation of the UN, the veto power was resented by many small countries, and in fact was forced on them by the veto nations - US, UK, China, France and the Soviet Union - through a threat that without the veto there would be no UN. Francis O. Wilcox, an adviser to US delegation to the 1945 conference described it: "At San Francisco, the issue was made crystal clear by the leaders of the Big Five: it was either the Charter with the veto or no Charter at all. Senator Connally dramatically tore up a copy of the Charter during one of his speeches and reminded the small states that they would be guilty of that same if they opposed the unanimity principle. "You may, if you wish," he said, "go home from this Conference and say that you have defeated the veto. But what will be your answer when you are asked: 'Where is the Charter'?"