Iran announced on Saturday that it had closed the Strait of Hormuz in response to continued Israeli airstrikes in southern Lebanon, claiming the strikes violated Clause 1 of the recently signed US-Iran memorandum of understanding — the provision requiring the “immediate and permanent termination of military operations on all fronts, including in Lebanon.” The US Central Command disputed the claim, with a spokesperson insisting traffic continued to flow and that “Iran does not control the Strait of Hormuz.” BBC Verify tracking data showed at least five tankers passed through on Saturday, though several vessels appeared to make U-turns. Meanwhile, Vice President JD Vance departed Washington for direct US-Iran talks in Switzerland, where Pakistan’s prime minister would also be present, having served as mediator throughout the wider conflict. Israel has stated it has no intention of withdrawing its forces from Lebanon.
The received wisdom
The optimistic reading — and it has been genuinely tempting — goes roughly as follows: the US-Iran ceasefire announced this month is a historic achievement, the product of shrewd dealmaking that ended a conflict threatening to engulf the entire Middle East. Iran’s supreme leader has been gravely weakened. The regime, its patron Hezbollah badly damaged, its nuclear programme set back, and its economy in ruins, has every incentive to honour the deal. The Strait closure is a negotiating gesture, not a real closure — the Americans say traffic is flowing, and Vance is already on his way to Zurich. Things are “actually getting better,” as Vance put it. The 60-day window for further talks gives both sides room to manoeuvre. The deal’s architecture, including its 14-point memorandum, is robust enough to absorb these early shocks. Optimists would add that Iran, having already closed the Strait once after the initial US-Israeli strikes in February, understands the economic pain the closure inflicts on China — Iran’s largest oil customer — and cannot afford to repeat the exercise for long.
A different read
The optimists are not wrong about the incentives, but they are reading the wrong map.
The structural problem with the US-Iran MOU is one that American diplomacy has repeatedly encountered in the Middle East: Washington negotiated a deal premised on a level of control over its ally, Israel, that it demonstrably does not possess. Clause 1 of the memorandum commits to a ceasefire “on all fronts, including in Lebanon.” Israel’s position is that the Lebanon conflict is categorically separate from the Iran war and that Israeli forces have no obligation to withdraw. That is not a peripheral technicality. It is the central interpretive dispute threatening to unravel the entire framework before the ink is dry.
This pattern has antecedents. The 1973 Yom Kippur ceasefire, brokered by Kissinger between Egypt and Israel, collapsed within days because neither superpower could fully restrain its client. The Taif Agreement of 1989 was supposed to end Lebanon’s civil war comprehensively; instead it froze the conflict’s underlying dynamics. American administrations across the political spectrum have signed agreements in the Middle East whose durability depended on cooperation from actors whose domestic political constraints were, to put it politely, underestimated.
Iran’s Strait closure — whether symbolically gestural or tactically real — is the regime’s way of forcing Washington to choose: pressure Israel on Lebanon, or watch the broader deal slowly corrode. It is a leverage play, and an effective one. The energy markets recognised it immediately. The Federal Reserve held interest rates this week partly because of uncertainty over energy costs traced directly to Hormuz volatility, and half of the Federal Open Market Committee’s members now project a rate hike before year-end. The economic transmission from Iranian brinkmanship to American household borrowing costs is not theoretical; it is running in real time.
Trump’s response — posting that the US could impose its own tolls on Strait of Hormuz shipping if no deal is reached — was, characteristically, more provocative than it was clarifying. It may be intended as pressure on Tehran, but it also signals to the Gulf states and to China that American commercial strategy in the waterway is in flux. That is not a reassuring signal to send in the middle of a fragile ceasefire.
The deeper problem is that Vance in Switzerland is negotiating a peace whose most combustible variable is a government in Jerusalem that is not at the table. Israel’s insistence that its Lebanon operations are legally and morally distinct from the Iran war is not frivolous — Hezbollah did fire rockets into Israel, and Israel has genuine security interests in southern Lebanon. But from Tehran’s perspective, the distinction is irrelevant. What matters is that the killing continues, the MOU’s most prominent clause is being visibly dishonoured, and the regime needs domestic cover for having signed a deal. Every Israeli airstrike that kills Lebanese civilians while the regime’s negotiators sit across from Vance in a Swiss hotel is a propaganda gift to the hardliners who opposed the deal.
The 60-day window for further talks is real, but time has a way of compressing in Middle Eastern crises. The question to ask is not whether both sides want the deal to hold — they probably do — but whether Washington has the leverage and the political will to enforce its own commitments on an ally that answers to a different set of domestic pressures.
What to watch
- Whether Vance extracts a commitment from Tehran to reopen the Strait in exchange for concrete US pressure on Israel’s Lebanon operations — the sequencing matters enormously.
- The dot-plot trajectory at the Federal Reserve: if energy prices spike further from Hormuz disruption, the nine FOMC members already projecting a rate hike become a majority, and the political consequences for the administration will be severe.
- Israeli domestic politics: the government’s position that Lebanon is a separate front has internal support, but any deal that requires Israeli withdrawal will face a coalition crisis. Watch whether the US applies financial or military-supply leverage.
- The 72-hour clock: Pakistan’s PM and Vance meeting in Switzerland means Sunday and Monday are the critical window. A failure to produce even a communiqué could accelerate the deal’s unravelling.
— J