H.R. 4281 — Bunker Buster Act of 2025

This section states 18 congressional findings concerning Iran's nuclear program, including its definition of high-enriched uranium (at least 20% uranium-235); breach of the 2015 Joint Comprehensive Plan of Action limit of 3.67% enrichment; production of uranium enriched to 60% (with a stockpile of 142.1 kilograms as of May 11, 2024, per IAEA report, sufficient for several nuclear bombs); overall enriched uranium stockpile of 6,201.3 kilograms; IAEA censures and violation declarations (including in June 2024 and June 12, 2025); installation of 1,400 advanced centrifuges at Fordow; and Iranian funding and arming of proxies including Hamas (over 5,000 rockets, missiles, and drones launched at Israel since October 7, 2023), the Houthis (at least 60 ship attacks since November 2023), and Hezbollah (over 100,000 missiles and rockets supplied).

This section states the sense of Congress that the United States should (1) seek to extend limitations on Iran's enriched uranium, including through multilateral diplomatic initiatives; (2) ensure that Israel and other allies are prepared for all contingencies if Iran pursues development of a nuclear weapon; (3) send a clear signal to Iran that development of a nuclear weapon will never be tolerated; and (4) reaffirm the U.S. commitment to deter Iranian nuclear development with a credible military threat.

This section authorizes the President, upon request by the Government of Israel and subject to preliminary conditions, to take actions to ensure Israel is prepared for all contingencies if Iran seeks to develop a nuclear weapon. Preliminary conditions require the President to certify to Congress that such actions are vital to U.S. national security interests and that specified conditions for transferring Massive Ordnance Penetrator (MOP) munitions—large bombs designed to destroy deeply buried targets such as underground nuclear facilities—are met, including Iranian noncompliance with its NPT Safeguards Agreement (i.e., the 1974 agreement with the International Atomic Energy Agency (IAEA) for safeguards under the Nuclear Non-Proliferation Treaty), the absence of alternative Israeli means to destroy Iran's underground nuclear infrastructure, and a dual-key control system requiring U.S. presidential approval (via the Secretary of Defense) prior to any Israeli deployment. The authorized actions are: (1) providing infrastructure in Israel to accommodate MOP systems, including extended runways for MOP-carrying aircraft, such aircraft, basing options, and munition storage facilities; (2) storing MOP or related munitions in Israel for U.S. use, or transferring them to Israeli custody upon meeting the conditions described above; (3) training Israeli personnel on MOP or related munitions; and (4) conducting joint research and development with Israel to enhance U.S. ordnance and develop Israeli capabilities to destroy underground infrastructure, including Hezbollah rocket storage and manufacturing facilities and Iranian nuclear facilities.