Hormuz traffic remains severely constrained as US-Iran contact fails to change military risk

Bottom Line

As of 23 September 2026, 0130Z, commercial traffic through the Strait of Hormuz is very likely to remain severely constrained through 25 September, at 85 per cent and moderate confidence. Partial movement remains likely at 70 per cent, while zero commercial tanker transits for 48 consecutive hours remains unlikely at 15 per cent. These probabilities are unchanged from the 22 September briefing.

The new reported Araghchi-Witkoff contact and Iran's conditional seven-day reopening offer increase the prospect of temporary deconfliction, but have not changed observed traffic. Houthi pressure against Saudi Arabia continues, but the material does not establish a complete Houthi blockade of Bab al-Mandab or a confirmed anti-ship attack against a non-Saudi commercial vessel.

The source mix is weighted towards the highest and usually reliable tiers, but includes official, state-media and party battlefield claims. Commercial tracking is useful for movement trends but differs by vessel definition and coverage. Official and state-media reporting is stronger for declared intent and own-force activity than for attribution, damage or territorial control.

Key Developments

Strait of Hormuz

Reported fact: One account recorded two vessels in Hormuz on 22 September. Kpler counted 17 commodity vessels over a recent weekend, compared with 37 the previous weekend and roughly 125 per day before the conflict. Saudi Arabia has restarted its East-West Pipeline, and Saudi Aramco has loaded about 14 million barrels onto seven supertankers inside the Gulf. The supplied material does not establish current pipeline throughput or the precise Yanbu terminal volumes.

Assessment: Commercial movement is very likely to remain below normal through 25 September. Severe restriction does not equal complete closure. Kpler and Windward data should be read alongside port-call and flag-state reporting because their vessel classifications differ. Confidence is moderate.

US-Iran contact

Reported fact: Major-media and wire reporting describes contact involving Iranian Foreign Minister Abbas Araghchi and US special envoy Steve Witkoff. Other accounts describe mediated exchanges rather than a confirmed face-to-face meeting. Iran has offered to reopen Hormuz within seven days if the United States eases military pressure and lifts the blockade on Iranian ports. Donald Trump has called for Iran's complete economic isolation.

Assessment: A temporary deconfliction arrangement by 26 September 0130Z has a roughly even chance, at 45 per cent and low to moderate confidence. A comprehensive agreement before 25 September is unlikely, at 15 per cent and moderate confidence. Public contact without a passage notification, port-access arrangement or naval deconfliction mechanism will not change the maritime judgement.

Houthi pressure

Reported fact: Saudi authorities reported interception of a ballistic missile directed towards Riyadh. Houthi statements claimed attacks on Riyadh and Saudi Aramco facilities at Yanbu and declared a naval blockade against Saudi Arabia. Reporting places Houthi forces in or near Mocha and Mayyun, but accounts conflict over physical control of those locations and Bab al-Mandab. UKMTO reporting in the prior cycle recorded multiple tanker incidents since 16 September, but responsibility remained unresolved.

Assessment: A Houthi missile, one-way attack UAV or explosive-boat attack attempt against a named Saudi facility or Saudi-linked maritime target by 7 October is likely, at 75 per cent and moderate confidence. An attempt against a non-Saudi commercial vessel is unlikely, at 25 per cent and low confidence. The material supports a demonstrated threat to Saudi land targets and declared maritime intent, not a verified blockade, mine campaign or successful anti-ship attack against non-Saudi commercial shipping.

Secondary developments

Reported fact: Israeli military activity continues in Gaza despite the ceasefire. Russian and Ukrainian forces continue reciprocal strikes. Foreign-supplied drones sustain operations by the Sudanese Armed Forces and Rapid Support Forces. JNIM and the Azawad Liberation Front continue pressure on FAMa and Russia's Africa Corps, while more than 900 fuel tankers reportedly reached Bamako under military escort on 14 September.

Assessment: Israeli military activity is very likely to keep the Gaza ceasefire operationally ineffective through 6 October, at 90 per cent and high confidence on direction. Sudan aid-access deterioration by 30 September is likely, at 75 per cent and moderate confidence. Russian and Ukrainian strike activity over the next 72 hours is very likely, at 85 per cent and moderate confidence. These updates affect the crisis index and humanitarian warning picture but do not alter the principal Hormuz assessment.

Analysis

The observed pattern is constrained maritime movement under unresolved military threat, not a verified formal closure. The traffic decline is compatible with commercial self-withdrawal caused by war-risk, force-protection and insurance concerns. It is also compatible with selective Iranian enforcement or incomplete tracking coverage. The present evidence favours commercial avoidance and selective passage because Kpler and Windward report sharp reductions while Saudi Aramco loading, residual tanker movement and US statements that lanes remain navigable indicate that some traffic continues.

Iran's reopening offer changes the diplomatic context but not the operational picture. A mutually accepted arrangement would need to specify which vessels could transit, how Iranian and US naval forces would deconflict, and whether Iranian ports would be accessible. The supplied material reports no such mechanism. The probability of temporary deconfliction has therefore increased, but the probability of normal traffic has not.

The Houthi assessment requires a distinction between intent, physical control and demonstrated capability. Houthi statements establish declared intent to pressure Saudi Arabia. Saudi reporting of an intercepted missile supports an ongoing threat to Riyadh, but does not independently prove the launcher's origin. Claims of attacks on Yanbu and Aramco facilities remain claims unless supported by imagery, operator reporting or independent damage assessment. Reports of Houthi presence in Mocha and Mayyun support a possible ability to monitor or threaten approaches to Bab al-Mandab, but conflicting accounts prevent a high-confidence assessment of territorial control. No supplied material confirms mine-laying or a successful attack on a non-Saudi commercial vessel.

The practical effects differ by stakeholder. Saudi Aramco and Iraqi oil exporters face reduced loading flexibility and uncertain access to Gulf tanker routes. The East-West Pipeline and Yanbu provide partial mitigation, but their current throughput is not established in the supplied reporting. Commercial tanker operators and the International Group of P&I Clubs face continued war-risk pricing and potential rerouting. Chinese refiners and other Asian buyers face delays, higher freight costs and uncertainty over replacement cargoes. CENTCOM and the US Navy face continued force-protection exposure around named bases, vessels and air-defence nodes. UN agencies face a separate access risk if the Adre authorisation expires without renewal.

Analytic continuity

Indicators & Warnings

• Hormuz traffic: Fewer than 10 Windward-classified commercial transits in each of two successive UTC 24-hour windows, excluding naval, fishing and duplicate AIS tracks, would raise the probability of a 48-hour zero-transit period from 15 per cent towards 25 to 35 per cent. More than 30 comparable transits per day would weaken the severe-restriction assessment. Collectors: Windward, Kpler, port-call data and flag states. Horizon: 24-72 hours.
• Deliberate enforcement: UKMTO, US Naval Cooperation and Guidance for Shipping, a flag state or commercial operator confirms a strike, boarding, mine, navigational warning or Iranian order affecting a named vessel. Iranian attribution would raise the near-total stoppage estimate. Horizon: 24-72 hours.
• Houthi anti-ship use: A confirmed Houthi missile, one-way attack UAV or explosive-boat attempt against a non-Saudi commercial vessel would raise the probability of sustained Bab al-Mandab disruption from 25 per cent towards 40 to 50 per cent. Collectors: UKMTO, vessel operators, commercial imagery and independent launch-track analysis. Horizon: 72 hours to 14 days.
• Bab al-Mandab fire control: Imagery or geolocated launch tracks showing Houthi sensors, launchers or resupply on Mayyun, near Mocha or on the western coast would increase confidence that the group can interfere with the traffic separation scheme. Collectors: commercial satellite providers, maritime patrol reporting and AIS analysis. Horizon: 7-14 days.
• Saudi export mitigation: Saudi Aramco, the Saudi Energy Ministry, Yanbu port records or tanker data provide daily East-West Pipeline flows, named terminal loadings or ship-to-ship transfer volumes. Increased non-Hormuz exports would lower energy-supply pressure; an outage or falling volumes would raise it. Horizon: 24 hours to 7 days.
• Commercial self-withdrawal: The International Group of P&I Clubs, war-risk underwriters, shipbrokers or major tanker operators issue circulars raising premiums, excluding Hormuz calls or routing vessels around the Cape of Good Hope. This would favour voluntary avoidance over formal closure and raise freight costs for Asian buyers. Horizon: 24-72 hours.
• Diplomatic implementation: Iran, the United States or a mediator publishes a mutually accepted passage, port-access or naval-deconfliction arrangement, followed by a sustained increase above 30 comparable transits per day. This would lower the 48-hour zero-transit probability below 15 per cent. Horizon: 72 hours to 7 days.
• US offensive preparation: CENTCOM or the US Department of Defence confirms strike authorisation, additional bomber or carrier movement, personnel evacuation or imminent offensive action. This would raise the probability of Iranian retaliation within 72 hours after a strike. Horizon: 24-72 hours.
• Sudan access: The UN reports that the Adre authorisation expires without renewal, cross-border convoys stop, or fighting cuts routes towards El Obeid and Kordofan. This would raise the probability of an aid-supply shock by 30 September. Horizon: By 30 September.

Alternatives

The first four scenarios below are mutually exclusive outcomes for commercial traffic by 26 September 0130Z. Their probabilities sum to 100 per cent. The final two are causal hypotheses and are not additive to the outcome probabilities.

Constrained partial traffic, 45 per cent, roughly even chance

At least one commercial transit occurs in each 24-hour period, with an average of 10 to 30 comparable transits per day. Residual movement, Saudi Aramco loading and the absence of verified mine or boarding activity support this outcome. The causal explanation is more consistent with voluntary commercial avoidance, force-protection concerns and selective passage than with a fully enforced Iranian closure.

Partial traffic below 10 comparable transits on at least one day, 25 per cent, unlikely

This outcome would fit further insurer withdrawal, a new unattributed incident or a temporary Iranian warning without a formal closure. It remains compatible with the 70 per cent partial-transit estimate because at least one transit occurs in each day. Kpler and Windward classification differences require cross-checking against port calls and AIS data.

Zero commercial tanker transits for 48 consecutive hours, 15 per cent, unlikely

A confirmed Iranian boarding, mine, repeated attack, formal navigation order or US-Iran strike exchange would increase this probability. Current residual movement and Gulf loading make complete cessation less likely than severe but incomplete restriction.

Negotiated selective passage above 30 comparable transits per day, 15 per cent, unlikely

The reported Araghchi-Witkoff channel and Iran's seven-day offer provide a possible pathway. Washington has not accepted Iran's conditions, and no implementation mechanism is reported. Public contact without verified traffic would not meet this scenario.

Tracking or classification error is the main cause of the apparent decline, low probability

This hypothesis would gain support if port-call records, satellite imagery and independent flag-state reporting showed normal commercial movement despite low tracker counts. Multiple commercial and media reports describe reduced traffic, so this is not the lead explanation, but the exact scale of the decline remains uncertain.

Iranian selective enforcement is the main cause of reduced traffic, low to moderate probability

This hypothesis would gain support from confirmed IRGC Navy boardings, explicit navigation orders, repeated diversions after warnings or evidence that selected states receive passage while others are denied. It remains the principal high-impact alternative because confirmed enforcement would rapidly increase insurer withdrawals and energy prices.

Outlook

Through 25 September, severe Hormuz restriction remains very likely at 85 per cent and moderate confidence. By 26 September 0130Z, at least one commercial transit in each UTC 24-hour period is likely at 70 per cent, while zero commercial tanker movement for 48 consecutive hours is unlikely at 15 per cent.

Through 6 October, the US-Iran confrontation is very likely to remain active at 80 per cent and moderate confidence. A new US strike is a roughly even chance at 50 per cent and low confidence. If a strike occurs, an Iranian attack on a named US base or interest within 72 hours is likely at 70 per cent and moderate confidence. The approximate unconditional probability of both events is 35 per cent, subject to dependence assumptions.

By 7 October, a Houthi attack attempt against a named Saudi facility or Saudi-linked maritime target is likely at 75 per cent and moderate confidence. An attack attempt against a non-Saudi commercial vessel is unlikely at 25 per cent and low confidence. Israeli military activity is very likely to keep the Gaza ceasefire operationally ineffective through 6 October. Sudan aid-access deterioration by 30 September is likely, but the exact scale depends on the Adre decision and the security of routes into Darfur and Kordofan.

CrisisBrief Index

Index: 66, HIGH.

Components: conflict 68, maritime trade 78, energy 65, political 45.

The provisional calculation weights conflict at 35 per cent, maritime trade at 25 per cent, energy at 25 per cent and political instability at 15 per cent. It produces 66.3 before rounding. The uncertainty range is 61 to 71. The score is broadly unchanged from the prior reported 66, although the prior briefing did not publish a reproducible calculation. The current score is driven by the active US-Iran confrontation, severe but incomplete Hormuz disruption, Houthi pressure against Saudi Arabia and persistent fighting in Gaza, Ukraine, Sudan and Mali. It remains below SEVERE because there is no verified complete Hormuz closure, no confirmed Houthi blockade of Bab al-Mandab and no evidence of unrestricted US-Iran regional war or a Taiwan blockade.