The announcement came as a high-level Iranian delegation departed for Switzerland for talks with US officials aimed at preserving the fragile agreement brokered by Pakistan earlier this week. However, Washington immediately disputed Tehran’s claim that the strategic waterway had been shut, saying commercial shipping continued uninterrupted through the strait.
In a statement carried by Iranian state television, the military command said the move was a response to what it described as Washington’s “clear breach of its commitments” under the agreement, which Tehran says requires an end to fighting “on all fronts”, including Lebanon. The statement described the closure as a “first step” and warned that “if the aggression continues, subsequent steps have been planned.”
Separately, Iran’s Islamic Revolutionary Guard Corps (IRGC) warned vessels against approaching the Strait of Hormuz, saying their security could be at risk. The group cited ongoing Israeli “crimes” in Lebanon and alleged US failures to enforce a ceasefire.
Mohammad Mokhber, an adviser to Iran’s Supreme Leader Ayatollah Mojtaba Khamenei, echoed the criticism, accusing Washington of failing to implement the first clause of the 14-point agreement. Writing on X, Mokhber said that as long as the deal remained “only on paper”, the flow of Middle Eastern energy would remain halted.
US rejects closure claim
The United States quickly pushed back against Iran’s announcement. “Iran does not control the Strait of Hormuz. Traffic continues to flow, and US forces are monitoring the situation to ensure this remains the case,” US Central Command spokesperson Captain Tim Hawkins said, news agency Associated Press reported.
CENTCOM said 55 merchant vessels carrying more than 17 million barrels of oil and other cargo transited the waterway on Saturday.
The Strait of Hormuz remains one of the world’s most critical energy chokepoints, handling roughly one-fifth of global oil and liquefied natural gas shipments. Any prolonged disruption could have significant implications for global energy markets, including India, which relies heavily on crude imports routed through the Gulf.
Momentum builds for Switzerland talks
Despite the latest tensions, diplomatic efforts appeared to be moving forward. Pakistan, which helped broker the interim agreement, said technical-level talks involving Iranian, American and Qatari representatives would begin on Sunday in Burgenstock, Switzerland.
Iranian state media reported that the delegation heading to Switzerland is led by Parliament Speaker and chief negotiator Mohammad Baqer Qalibaf and includes Foreign Minister Abbas Araghchi, along with senior security, central bank and oil officials.
Iranian Foreign Ministry spokesperson Esmail Baghaei said Tehran would use the talks to press Washington to fulfil its obligations under the agreement.
“Negotiations toward a final agreement will begin only once key commitments are upheld,” Baghaei said, warning that otherwise “the memorandum of understanding as a whole will be jeopardized.”
JD Vance expected to travel to Switzerland ‘soon’
US Vice President JD Vance indicated he would travel to Switzerland soon and expressed confidence that the ceasefire framework would survive.
“I expect that I will leave sometime in the next couple of days, but it’s always a delicate coordination dance and the diplomatic protocols,” Vance told Fox News.
Vance added that senior US negotiators Jared Kushner and Steve Witkoff had already arrived in Switzerland and were working through the technical details of anticipated talks on Iran’s nuclear programme.
“My understanding, talking to Jared and Steve this morning, is things are going well,” he said.
Lebanon violence casts shadow over agreement
The diplomatic efforts come against the backdrop of continued fighting in Lebanon, which has emerged as the biggest threat to the agreement.
Lebanese Civil Defence said at least 20 people were killed in Israeli strikes on Saturday, hours after a ceasefire came into effect, news agency Reuters reported. Earlier reports from Associated Press had put the death toll at 16, including two children.
Lebanon’s state news agency NNA reported that Israeli warplanes and drones struck locations across southern Lebanon and the Bekaa Valley, both Hezbollah strongholds.
An Israeli military official said Hezbollah fired more than 50 projectiles at Israeli forces overnight, prompting retaliatory strikes on what Israel described as Hezbollah targets.
Israel said it remained committed to the ceasefire but would continue acting against any threat to its forces or civilians.
“Hezbollah’s attacks constitute repeated violations of the ceasefire agreement,” the Israeli military said in a statement.
Hezbollah, meanwhile, accused Israel of repeatedly violating the truce and said it would not allow Israel “freedom of movement” in occupied Lebanese territory.
A senior Hezbollah official told AP that Iran had informed the group it would not reopen the Strait of Hormuz until Israel publicly committed to a comprehensive ceasefire in Lebanon and halted military operations there.
The official said Hezbollah would also honour the ceasefire if Israel did.
A fragile truce at risk
The latest violence underscores the challenge facing the broader US-Iran understanding announced this week.
Neither Israel nor Hezbollah are signatories to the memorandum, which calls for an immediate halt to military operations across several fronts, including Lebanon.
Israeli Prime Minister Benjamin Netanyahu has vowed to keep Israeli forces in southern Lebanon until all threats against Israel are eliminated. Israeli broadcaster Channel 12 reported that Netanyahu and Defence Minister Israel Katz instructed the military to hold fire but would not withdraw from territory already captured.
Hezbollah, meanwhile, insists it will not stop attacks unless Israel withdraws from Lebanese territory — a condition Iran has also linked to the success of the agreement.
The toll from the latest conflict continues to mount. Lebanon’s health ministry says 4,057 people have been killed in Israeli attacks since March 2, including women, children and medical personnel, though it does not distinguish between civilians and combatants. Israeli authorities say at least 32 soldiers and four civilians have been killed in fighting with Hezbollah.
Residents on both sides of the border expressed scepticism about the ceasefire.
“All night we heard explosions. We got kind of excited by those statements about a ceasefire, but everything is continuing as usual,” Ofri Valfer, a resident of northern Israel, told Reuters.
What happens next?
The Switzerland talks are expected to focus on implementing the memorandum signed earlier this week, which launched a 60-day process for negotiations on Iran’s nuclear programme, sanctions relief and broader regional security arrangements.
The United States has already lifted its blockade on Iranian ports and resumed allowing Iranian oil exports under the interim deal, while provisions covering sanctions relief and the unfreezing of Iranian assets remain under discussion.
But with fighting continuing in Lebanon, Iran threatening renewed disruption in the Strait of Hormuz, and both sides accusing each other of violating commitments, the diplomatic breakthrough faces its first major test.
(With inputs from Reuters, AP)
People gather at the site of a destroyed building that was hit in an Israeli airstrike in Qannarit village, southern Lebanon, Saturday, June 20. (AP Photo) 
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