Uranium is typically enriched to 90% U-235 or higher (commonly called "weapon-grade uranium") for use in nuclear weapons (Center for Arms Control and Non-Proliferation, Union of Concerned Scientists). Iran promised to curtail uranium enrichment to less than 4% as part of the 2015 Iran nuclear deal (i.e., the “Joint Comprehensive Plan of Action” or “JCPOA”), but it stepped back from these commitments in retaliation for attacks on Iranian leaders and the U.S. withdrawal from the agreement (Council on Foreign Relations, U.S. Institute of Peace). Following the U.S.' withdrawal, China, France, Russia, the United Kingdom, Germany, the European Union, and Iran remained participants in the JCPOA. 

Although Iran has increasingly limited monitoring and verification of its nuclear program, the International Atomic Energy Agency (IAEA) continues to report on its JCPOA commitments (Reuters, Politico). In February of 2023, it reported that it had found particles containing up to 83.7% enriched uranium (IAEA, NBC).