Office Home Office Home About Us HomeBureaus & Offices > Bureau of International Security and Nonproliferation ...Office of Multilateral Nuclear and Security Affairs hide Office of Multilateral Nuclear and Security Affairs Our Mission The Office of Multilateral Nuclear and Security Affairs (ISN/MNSA) leads Department of State formulation and implementation of U.S. policy relating to the global nuclear nonproliferation regime, especially the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the NPT review process, the International Atomic Energy Agency (IAEA), Nuclear-Weapon-Free-Zone treaties and protocols, and nuclear-related security assurances.