The United States and Iran continue to make competing claims about who has greater control of the critical Strait of Hormuz in the Gulf.
Washington claims the strait is open and that dozens of ships, carrying millions of barrels of oil, are passing through each day. US President Donald Trump claimed last month that the US was in “total control” of the waterway, through which one-fifth of the world’s oil and gas is shipped during peacetime, but which has been closed since the US-Israel war on Iran began six months ago.
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Iran, however, says the strait remains under its control and is closed except to pre-approved vessels using its designated channels. It has warned that other ships attempting to transit risk being targeted.
So what is really going on in the strait – and what explains the divergent accounts?
What are the latest US claims about the Strait of Hormuz?
The US says shipping through the Strait of Hormuz has significantly increased in recent weeks.
Two US officials told CNN that 40 commercial ships carrying some 18 million barrels of oil passed through the strait under US military escort on Tuesday, in what would be a new wartime record.
Trump gave a similar figure on Monday, saying the US Navy was helping some 30 ships pass through Hormuz every night. He later said the waterway was “under USA control”.
In terms of oil, US Treasury Secretary Scott Bessent said that “at least 10 million barrels” were getting through the strait each day, with between 15 million and 17 million on Tuesday.
The assessment comes after US CENTCOM commander Brad Cooper claimed last week that the US military had cleared Hormuz’s transit lanes of sea mines.
Before the war began, an average of around 100 ships and 20 million barrels of oil are estimated to have passed through the waterway each day.
According to figures from PortWatch, this has fallen to an overall average of seven vessels since March.
What does Iran claim about the strait?
Iran has acknowledged that some vessels are getting through the strait, but insists it remains in control of the waterway.
Iran’s Parliament Speaker Mohammad Bagher Ghalibaf on Tuesday said “the enemy managed to get some ships” through Hormuz, but stressed that Iranian forces remain “in complete control of the strait and will not allow it to be opened”.
Ghalibaf accused the US of giving ships “false guarantees” about their ability to cross a southern route in Hormuz, warning that ships that try to do so would be targeted.
The following day, Iran’s Islamic Revolutionary Guard Corps (IRGC) claimed two oil tankers had hit mines and were disabled while trying to cross an “illegal route” in the strait. Saudi Arabia, meanwhile, claimed an Iranian attack hit a Saudi oil tanker, killing two Filipino sailors.
What does shipping data show?
The latest ship-tracking data paints a different picture than the US claims, with far fewer vessels recorded as transiting the strait.
According to marine analytics firm Kpler, just six vessels crossed the strait on Wednesday, 11 on Tuesday and five on Monday. It put the 10-day average at 13 vessels per day.
Other ship-trafficking services show a similar pattern. Maritime data firm Lloyd’s List Intelligence recorded an average of around 12 transits per day from August 26 to September 1, though the latest data may be incomplete “due to a lag in identifying dark transits”, said the firm’s maritime intelligence and research director, Bridget Diakun. This means that some ships are switching off their tracking beacons.
From August 17-23, Lloyd’s List Intelligence recorded “about 14 non-Iranian-linked ships each day”, Diakun told Al Jazeera.
All these figures are far lower than the US claim that 40 ships transited the strait on Tuesday.
The Joint Maritime Information Center (JMIC), which monitors threats to shipping in the region, said in a September 1 advisory that commercial traffic through Hormuz was “far below baseline”, despite a “modest uptick from recent lows”.
The advisory put the risk level for Hormuz at “severe”, citing a “continued risk of drifting or uncharted mines”, despite US claims to have cleared the strait of mines.
What explains the discrepancy?
Diakun told Al Jazeera that it is difficult to explain the gap between US-claimed transit figures and those recorded by ship trackers without insight into how the US tallies its own figures.
She said it’s possible the US includes smaller or non-cargo-carrying ships in its total, unlike Lloyd’s, which only counts “cargo-carrying vessels over 10,000 dwt [deadweight tonnage]”.
Eirik Hooper, a senior associate covering the ports and terminals sector for maritime research consultancy Drewry, also pointed to possible differences in how the US counts vessel transits.
“A US operational count plausibly includes everything that moved under or near naval protection: naval auxiliaries, offshore support and tugs, coastal and small craft [and] dhows,” said Hooper, noting that ship-tracking firm Kpler filters out such vessels “on size or cargo grounds”.
Hooper also said the US has access to “satellite, airborne and other sensor coverage plus its own convoy manifests”, which enables it to see vessels not immediately picked up by the normal automatic identification system (AIS) tracking system.
“By late August, the majority of Hormuz crossings were classified ‘dark’ or unknown by route, and AIS data counts often need to be revised to include vessels that switch off their transponders, with confirmed movements backdated,” said Hooper.
More generally, both the US and Iran have an incentive to play up their influence in the strait, the status of which has become a major sticking point in their six-month conflict.
Former US Ambassador Henry Ensher recently told Al Jazeera that he believes the latest cycle of US-Iran confrontation was likely triggered by CENTCOM’s claims to have de-mined that strait, and said “both sides would be well served to stop talking quite so much”.
