President Donald Trump has vowed to withdraw the US from the July 2015 Joint Comprehensive Plan of Action, or the "nuclear agreement", and reimpose sanctions on Iran unless it is renegotiated.

He wants the removal of the agreement’s sunset clauses, curbing of Iran’s ballistic missile program and regional influence, and more intrusive inspections of Iran’s nuclear and military facilities. Tehran has rejected any renegotiation of the signed multilateral agreement, which continues to be backed by the other four permanent members of the UN Security Council, plus Germany.

The JCPOA materialised after nearly two years of hard-hitting negotiations. The US and Iran had to move substantially from their original positions. Washington abandoned its insistence on Iran foregoing its entire nuclear

program, and Tehran gave up its resolve to continue its uranium enrichment at a high level. Tehran also agreed to allow expanded IAEA oversight, to reduce dramatically its stockpile of enriched uranium and its centrifuges, and not to build heavy water nuclear reactors for the next 15 years. In return, the other signatories agreed to lift all the nuclear-related sanctions against Iran.

The UN Security Council unanimously adopted Resolution 2231 endorsing the agreement on 20 July 2015, lifting all UN sanctions. The US supported the resolution, but maintained sanctions linked to alleged Iranian support of terrorism and human rights violations.