US President Donald Trump has promised an "economic D-Day" of sanctions against Iran, nearly six months into a conflict that has settled into a stalemate with neither a military breakthrough nor a negotiated settlement in sight. The move reflects growing frustration within the administration that its existing strategies have failed to force Iran to capitulate, and marks an attempt to widen pressure by targeting third countries that continue to trade with Tehran, rather than simply intensifying sanctions already in place since 1979.

Treasury Secretary Scott Bessent is due to unveil the detailed plans at a news conference on 24 August, but has warned that any nation still buying Iranian oil, transferring money or conducting seaborne transfers with Iran will face the "full might" of the US Treasury. Vice-President JD Vance called it a "new phase" of the conflict in which economic pressure is the most effective tool available. Experts, including a former Office of Foreign Assets Control official, said the strategy likely aims to widen the "economic blast radius" by threatening secondary sanctions against countries whose economies rely on the US dollar, building on the existing "Operation Economic Fury" campaign of Treasury sanctions and a naval blockade of Iranian ports.