Thomas G. DiNanno
Under Secretary of State for Arms Control and International Security
Thomas G. DiNanno has served as the 19th Under Secretary of State for Arms Control and International Security since October 2025. He previously held senior roles at the US Department of State, including Deputy Assistant Secretary and Senior Bureau Official in the Bureau of Arms Control, Verification and Compliance (AVC), where he oversaw policy on nuclear arms control, strategic stability, missile defence, and outer space. In this capacity, he led the 2020 negotiations on the New START Treaty with the Russian Federation and played a central role in US extended deterrence engagements with Japan, the Republic of Korea, and Australia. He also led the 2019 US–China Space Security Dialogue in Beijing and headed US delegations to the Organisation for the Prohibition of Chemical Weapons and the Conference on Disarmament.
Updated: May 6, 2026