The 15 member body has five permanent members (China, France, Russian Federation, the United Kingdom and the United States), and ten non-permament members, elected by the General Assembly for two-year terms.
Each country holds the Presidency of the Council for one month, alternating in an alphabetical order.
The veto power
Each Council member has one vote. Decisions on procedural matters are made by an affirmative vote of at least nine of the 15 members. Decisions on substantive matters require nine votes, including the concurring votes of all five permanent members. This is the rule of "great Power unanimity", often referred to as the "veto" power.
Under the Charter, all Members of the United Nations agree to accept and carry out the decisions of the Security Council. While other organs of the United Nations make recommendations to Governments, the Council alone has the power to make decisions which Member States are obligated to carry out.
When a complaint concerning a threat to peace is brought before it, the Council's first action is usually to recommend to the parties to try to reach agreement by peaceful means. In some cases, the Council itself undertakes investigation and mediation. It may appoint special representatives or request the Secretary-General to do so. It may set forth principles for a peaceful settlement.
When a dispute leads to fighting, the Council's first concern is to bring it to an end as soon as possible. On many occasions, the Council has issued cease-fire directives which have been instrumental in preventing wider hostilities.
It also sends United Nations peacekeeping forces to help reduce tensions in troubled areas, keep opposing forces apart and create conditions of calm in which peaceful settlements may be sought. The Council may decide on enforcement measures, economic sanctions (such as trade embargoes) or collective military action.
A State which is a Member of the United Nations but not of the Security Council may participate, without a vote, in its discussions when the Council considers that that country's interests are affected.
Both Members of the United Nations and non-members, if they are parties to a dispute being considered by the Council, are invited to take part, without a vote, in the Council's discussions; the Council sets the conditions for participation by a non-member state.