Question

which organ is responsible for maintaining peace and security among countries

Answer 1

an organisation called United Nations is responsible for maintaining peace and security among countries

Answer 2

Security Council

The Security Council  takes the lead in determining the existence of a threat to the peace or an act of aggression. It calls upon the parties to a dispute to settle it by peaceful means and recommends methods of adjustment or terms of settlement. Under Chapter VII of the Charter, the Security Council can take enforcement measures to maintain or restore international peace and security. Such measures range from economic sanctions to international military action. The Council also establishes UN Peacekeeping Operations and Special Political Missions