Treasury Secretary Scott Bessent has warned that the United States is preparing what he called the ‘single greatest financial offensive ever’ against Iran as the U.S.-Israel conflict enters what he described as its endgame.

Bessent went on to say that Washington intends to sever every economic lifeline supporting Iran’s government and isolate any country that continues conducting business with Tehran. He characterized the coming campaign as an ‘economic D-Day’, although the specific measures were expected to be announced later.

Iran dismissed the threat and warned that it could halt all regional oil exports if the war continues. Mohsen Rezaei, leader of Iran’s Supreme National Security Council, said any country supporting the American measures would be committing an act of war. Tehran also warned vessels not to enter the Strait of Hormuz without permission.

The strait normally carries about one-fifth of the world’s oil and gas but has been blocked since fighting began in February. Iran’s rial fell to a record low following Bessent’s announcement.

An economic threat of such weight would extend the confrontation far beyond Iran, effectively forcing banks, companies, and governments to choose between access to the American financial system and continued business with Tehran. Because many international transactions rely on U.S. dollars or on institutions with U.S. ties, it’s a threat that carries substantial consequences.

But Iran’s counter-threat shouldn’t be dismissed, either. The Strait of Hormuz is one of the world’s most important energy corridors, carrying about 20% of global oil and gas. An even longer blockage than we have been experiencing could tighten supply, drive up insurance costs, and deepen inflation. Any subsequent military attempts to reopen the waterway would also likely just exacerbate an already delicate situation.

While the strategy may weaken Iran’s ability to finance its government and military operations, sweeping isolation can intensify hardship for ordinary Iranians by reducing trade and weakening the rial. Success will therefore depend on whether the pressure changes Tehran’s behavior before economic retaliation and regional escalation inflict greater damage. Bessent’s announcement shows that Washington is preparing to treat Iran’s remaining commercial partners as participants in the conflict rather than neutral businesses.

Higher fuel costs are among the quickest and most talked-about economic effects. Rising fuel prices affect most businesses, either directly or indirectly. Continued instability in the region will likely result in higher flight costs, and businesses will have to absorb them or pass them on to consumers.

Iran is not likely to sit idly by, as its government has previously used cyberattacks and proxy forces to pressure its enemies without engaging them directly. Banks and transportation networks, as well as major companies, could become targets as Tehran seeks to impose costs on the United States.

Regardless of the severity or ultimate success of these attacks, they are potential actions by a hostile foreign government, so appropriate security measures will need to be taken.