Fewer than 20 commodity vessels transited the Strait of Hormuz over the weekend, shipping data showed on Monday, as Iranian and US blockades continue to restrict traffic through the waterway, one of the world's most important chokepoints for energy shipments, Reuters reported. Visible traffic through the strait sank to its lowest level in weeks, though last week's reporting on a US-organised corridor along Oman's coast suggests the real picture of physical supply may be less stark. The strait normally carries about a fifth of the world's oil — roughly 20 million barrels a day in a typical year, according to the US Energy Information Administration — and there is no maritime route around it, which is why even small shifts in visible traffic are watched so closely.

Initial data from shiptracker Kpler, cited by Reuters, showed four vessels crossing the strait on Sunday and 13 on Saturday. The figures are subject to revision, however, because some ships switched off their transponders during their passage, making them invisible to standard tracking.

The sub-20 weekend tally is a sharp step down even by the standards of a strait already operating under dual blockade, and it adds a fresh data point to an already contested picture of who actually controls the flow through the waterway. The count also landed at a pointed moment in the wider standoff: the same day Treasury Secretary Scott Bessent is due to unveil the toughest US sanctions yet on Iran, and hours after Mohsen Rezaei, secretary of Iran's Supreme National Security Council (SNSC), threatened to halt all Gulf oil exports entirely.

Reporting last week found that more than 80% of liquid cargo transiting Hormuz over a prior two-week period either used the Omani route along the southern side of the strait or traveled with transponders switched off — a pattern that shipping analysts said pointed to Iran having lost significant control over traffic despite its blockade.

For several weeks, the US military has been quietly operating a corridor along the Omani coast, helping to move about 10 million barrels of oil a day, with 15 to 20 tankers entering and leaving the strait nightly through a southern channel coordinated by a task force run from Fort Bragg. That corridor has effectively taken on the job of keeping Gulf crude moving because the only physical alternatives to Hormuz are overland pipelines — Saudi Arabia's East-West line to Yanbu and the UAE's export line to Fujairah, whose combined nameplate capacity of roughly 7 million barrels a day falls well short of the strait's normal throughput. US officials have said the operation has helped transport more than 660 million barrels of crude through the strait since early May, and President Trump has previously described the broader US naval blockade of Iran as fully effective.

The low visible transit count therefore sits awkwardly alongside those earlier claims. Sunday's tally of four vessels and Saturday's 13 compare with nightly movements of 15 to 20 tankers through the southern channel alone, according to the US description of the corridor. The disparity most likely reflects the extent to which shipping is now moving outside standard transponder tracking rather than a genuine collapse in physical flow, and the gap between transponder-based counts and actual movement suggests the low weekend number likely overstates the real disruption to physical supply — even as it reinforces the risk premium embedded in Brent and WTI.

Iran, for its part, has continued to assert authority over the waterway through its own mechanisms. These include a parliamentary bill approved last week allowing fees to be charged on vessels for navigation, environmental, fueling, insurance and safety services, as well as warnings from the country's Persian Gulf Strait Authority that vessels violating its declared transit arrangements face fines, seizure or confiscation.

The weekend figures also carry weight in the broader diplomatic picture. Bessent is due on Monday to announce what he has called the “toughest sanctions in history” against Iran, part of the economic pressure campaign that Trump has termed an “economic D-Day.” Rezaei warned over the weekend that if the pressure campaign continues, Iran would halt all oil exports through the strait and the wider Persian Gulf, and that any country cooperating with the US sanctions would be treated as an act of war.

Whether the reduced weekend vessel count reflects genuine tightening ahead of that threat, further concealment of actual traffic, or simple weekend scheduling variance is not yet clear from the available shipping data, and Kpler's initial counts could still shift as later data captures ships that ran dark during their passage. The concrete markers from here are the detail of Bessent's sanctions package, any enforcement action that follows Iran's new fee legislation and the Persian Gulf Strait Authority's warnings, and harder numbers on the Omani corridor's current throughput. With Rezaei's export-halt threat now sitting alongside a shrinking visible transit count, the setup points toward continued elevated volatility rather than a clean directional signal.

Related coverage:

• Bessent to unveil toughest Iran sanctions as Rezaei threatens total oil halt
• Iran dismisses new US sanctions as desperate as Hormuz shipping standstill continues