US-Iran talks begin in Switzerland as Tehran says it closed Strait of Hormuz

What Happened

On Saturday, Iran announced via its military that it had closed the Strait of Hormuz in response to Israeli attacks on southern Lebanon, accusing the United States of violating a 14‑point bilateral memorandum of understanding—specifically the first clause requiring ‘the immediate and permanent termination of military operations on all fronts, including in Lebanon.’ The US Central Command (Centcom) spokesperson, Tim Hawkins, disputed the claim, stating that ‘traffic continues to flow’ and that US forces are ‘monitoring the situation to ensure this remains the case,’ while adding that ‘Iran does not control the Strait of Hormuz.’ BBC Verify tracking data indicated at least five tankers passed through the strait on Saturday, though several vessels appeared to have made U‑turns; Centcom reported that commercial ship traffic had increased, with 55 merchant ships transiting. The announcement came after Israeli airstrikes killed at least 20 people in southern Lebanon less than 24 hours after a fresh ceasefire between Israel and Hezbollah was declared, and as both sides accused each other of repeatedly violating that truce. Israel’s military said it struck ‘dozens’ of Hezbollah targets after the group fired more than 50 projectiles at Israeli forces, and an Israeli soldier was killed in battle. Lebanon’s health ministry said 4,057 people had been killed since the conflict restarted on 2 March. Simultaneously, US Vice‑President JD Vance departed Washington for direct US–Iran talks in Switzerland on Sunday, aiming to make progress on ‘the nuclear issue’ and a ‘Lebanon ceasefire issue.’

Key Actors

Why It Matters

The Strait of Hormuz is a critical chokepoint for global energy, with about 20% of world oil and LNG transiting daily. Any prolonged disruption would send shockwaves through energy markets. Iran’s claim—and the US denial—highlights the fragility of the nascent US–Iran deal and the risk that Israeli–Hezbollah hostilities could unravel a broader diplomatic framework that also encompasses Iran’s nuclear programme. The parallel dispatch of Vice‑President Vance to Switzerland for direct talks underscores the high stakes and the Biden administration’s effort to de‑escalate on multiple fronts simultaneously.

Watch For

Monitor the US–Iran talks in Switzerland on Sunday for any concrete progress on the nuclear file or a Lebanon ceasefire. Track Centcom and commercial shipping data for further evidence of Strait of Hormuz traffic disruptions. Watch whether the US follows through on former President Trump’s threat to impose tolls on strait shipping. Observe the adherence to or further violations of the Israel–Hezbollah ceasefire, and any impact on the 60‑day window for finalising the broader US–Iran agreement.