An oil tanker and cargo ship remain anchored off the coast of Port Sultan Qaboos in Muscat, Oman, on June 21, 2026. The Strait of Hormuz, a key shipping route for oil and gas in the region, has been effectively closed since war broke out between the United States and Iran in late February. On Sunday, U.S. Vice President J.D. Vance arrived in Switzerland for high-level talks with an Iranian delegation as the two countries seek to clarify terms for ending the war.
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Shipping through the Strait of Hormuz ground to a halt over the weekend after Iran announced it had once again closed the world’s most important oil chokepoint, according to maritime information firm Windward.
The update came as industry trackers showed Iranian tankers continued to navigate the Strait, a narrow waterway that typically handles about 20% of global oil shipments.
Oil tanker traffic through the strait picked up soon after the United States and Iran signed a 14-point memorandum of understanding (MOU) last week, but the latest data shows it is already at an impasse.
A total of 12 ships passed through the Strait of Hormuz on Sunday, down from more than 21 the day before, according to an analysis published by Windward. Five of the eight ships that entered the area went dark, which is when the vessels disable their Automatic Identification System (AIS) transponders to hide their location, identity and destination.
“The current traffic situation is bleak, with sanctions, and ties to Iran, resembling a late-blockade baseline rather than a functioning open channel,” Windward said in a social media post Sunday.
Trade information firm Kupler said last week that at least 20 tankers passed through the Strait of Hormuz on Thursday, reflecting the highest level of traffic since June 2. This is still far below pre-war levels, when more than 100 ships, including dozens of tankers, were passing through the strait every day.
A separate analysis published Monday by maritime expert Lloyd’s List also found that commercial traffic continued to pass through the Strait of Hormuz over the weekend, contradicting Iran’s claims that it had closed the waterway again.
Iran said on Saturday it had closed the strategic strait, citing a cease-fire violation after Israel continued deadly attacks in southern Lebanon.
The US military has denied these claims, saying the waterway remains open and “Iran does not control the Strait of Hormuz.”
As of Saturday night, at least 15 Iranian-flagged Suezmax ships and very large crude carriers (VLCCs) had set sail from the Gulf of Oman with their AIS signals active, according to Lloyd’s List.
US and Iran meet in Switzerland
The United States and Iran held talks on Sunday at a Swiss mountain resort, building on a memorandum of understanding that both sides signed on Wednesday.
During the talks, the two parties are said to have made progress towards reaching a final agreement within 60 days, including agreeing to set up a commission or mechanism to end hostilities in Lebanon.
A senior Pakistani and Iranian official involved in the Burgenstock talks told MS NOW that the talks lasted into the early hours of the morning and were “constructive but tense.”
Under the memorandum, the two sides agreed to keep the Strait of Hormuz free for at least 60 days and cease all hostilities, including in Lebanon, where fighting continues between Israel and Iran-backed Hezbollah.
Iranian Foreign Minister Abbas Araghchi said his country had secured an exemption for exports of oil and petrochemical products, the lifting of port blockades, the release of some frozen assets and the start of a reconstruction and development plan.
President Donald Trump had hinted at further attacks on Iran ahead of the meeting in Switzerland. “Iran must immediately stop its highly paid proxies in Lebanon from stirring up trouble. If they don’t, we will hit Iran very hard again. Just like last week, and even harder!!!” President Trump said in a social media post on Sunday.
A large commercial ship and a small boat sail off the coast of Bandar Abbas, a port city in southern Iran, on June 21, 2026.
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Vice President J.D. Vance, who led the U.S. delegation to the talks, said he was optimistic about the outcome of the Swiss talks despite Iran’s recent threat to close the Strait.
He also downplayed the impact of the violence in Lebanon, saying progress had been made towards ending hostilities in Lebanon. “Things like this are always a little tricky,” Vance said.
—CNBC’s Anniek Bao and Spencer Kimball contributed to this report.
