Strait of Hormuz: The real oil-supply risk behind Iran’s pressure

Why this narrow waterway carries such weight

The Strait of Hormuz lies between Oman and Iran, linking the Persian Gulf with the Gulf of Oman and the Arabian Sea . The U.S. Energy Information Administration describes it as one of the world’s most important oil chokepoints .

The numbers explain why. In 2024, oil flows through the strait averaged 20 million barrels a day, equal to about 20% of global petroleum liquids consumption . The EIA also notes that the strait is deep and wide enough for the world’s largest crude oil tankers — but that if it were closed, there would be very few alternative routes to move oil out of the Gulf .

That combination is what makes Hormuz unusually sensitive: high volumes, limited workarounds and a shipping environment where delays or uncertainty can matter almost as much as physical blockage .

A claim of control is not the same as a lasting closure

Iranian pressure or a political claim over the strait does not automatically stop global oil supply. The risk escalates when that pressure begins to shape real vessel movement — for example through selective access, controlled corridors or reduced visibility of tanker traffic .

Windward, a maritime intelligence firm, reported on March 26, 2026, that Strait of Hormuz transit remained “constrained but is scaling,” with five AIS-visible crossings and additional semi-dark movements . AIS refers to the tracking signals used to monitor ships; when movements are less visible, the operating picture becomes harder to read.

The same Windward report said transit was increasingly being routed through a controlled northern corridor near Larak Island rather than normal open navigation lanes, and that Iran was formalising a selective-access system prioritising outbound energy flows and inbound essential goods .

A few days earlier, on March 22, Windward described Strait of Hormuz traffic as “near collapse,” with only 16 AIS-visible crossings recorded over the previous seven days . It also said transit was becoming increasingly selective and controlled, with some vessels rerouting through Iranian territorial waters .

Those reports should not be treated as proof of a permanent total shutdown. They do, however, show how the strait can become risky even while some shipping continues .

What oil markets are really afraid of

For oil markets, the fear is not only the immediate loss of barrels. It is the loss of confidence in a route that normally handles enormous volumes.

When a waterway moved an average of 20 million barrels a day in 2024, and when alternatives are limited, even partial disruption can become an energy-security problem . Buyers need to know whether cargoes will arrive. Shipowners need to judge whether voyages are safe. Traders need to price risk. If the route is technically open but access is selective or tracking is unclear, uncertainty rises .

That is why the warnings have been so stark. In an interview published by Le Monde, International Energy Agency Executive Director Fatih Birol described a closure of the Strait of Hormuz as the “greatest global energy security threat in history” . The severity of that warning reflects Hormuz’s role as the maritime link between Gulf energy exports and global markets .

This does not mean every threat will trigger a full-scale oil shock. But falling AIS-visible crossings, controlled routing and semi-dark movements are exactly the kinds of signals that make the market nervous .

For shipping, predictability is security

Maritime security in the Strait of Hormuz is not only about warships, missiles or official statements. For commercial shipping, the core question is practical: can vessels pass on a predictable route, at a predictable time, with enough transparency for operators to assess risk?

Windward’s reports point to several stress signals: a controlled northern corridor, selective access, semi-dark movements and a sharp reduction in AIS-visible crossings . Together, they suggest a move away from ordinary open-lane navigation toward a more managed and less transparent transit environment .

That may sound less dramatic than a full blockade, but for tanker trade it is still serious. Tanker movements depend on timing, routing and visibility. When those weaken, cargo scheduling and risk assessment become harder .

Could Iran control the strait for long?

The balanced answer from the available sources is: Iran can create disruption, but long-term, full and sustainable control would be difficult .

An analysis by the Al Jazeera Centre for Studies argues that reopening the Strait of Hormuz may be militarily possible, but would likely be costly and time-consuming . It also says persistent threats to shipping could take weeks or months to suppress, making long-term control impractical .

That points to a more realistic scenario than a single, clean “closure” event: repeated disruption. Traffic may fall, corridors may be controlled, some movements may become harder to track, and each episode can send a fresh jolt through shipping and energy markets .

Signals to watch next

The most important indicators are not just official statements. They are operational signs in the shipping data and energy-security warnings:

• A sharp and sustained fall in AIS-visible crossings
• Use of controlled corridors instead of open navigation lanes
• More semi-dark vessel movements, reducing visibility
• Selective access that prioritises some cargoes or routes over others
• Stronger closure-related warnings from energy-security agencies or market watchdogs

Bottom line

Yes, Iran’s pressure around the Strait of Hormuz can pose a major risk to global oil supply and maritime security. The reason is structural: in 2024, the strait carried an average of 20 million barrels a day, and there are few alternative routes if it is closed .

But a claim of control and durable full control are not the same thing. The evidence points to a more nuanced danger: Iran may struggle to keep the strait fully closed for the long term, yet it can still create serious disruption through controlled transit, selective access and reduced visibility .

For oil markets, that may be enough. In a chokepoint as important as Hormuz, uncertainty itself becomes part of the supply risk.