Iranian tankers test Gulf blockade

Two fully laden Iranian tankers have slipped out of the Persian Gulf with their tracking signals muted, underscoring how Tehran’s oil trade is adapting to a tightening US-led maritime squeeze even as warships, seizures and threats of interception raise the stakes across one of the world’s most critical energy corridors. Reports circulating on Wednesday said the vessels were part of a broader flotilla that has moved millions of barrels of crude despite the blockade, highlighting both the resilience of Iran’s export network and the limits of coercive enforcement at sea.

The development points to a hardening contest between Washington’s effort to choke off Iran’s maritime trade and a sanctions-evasion system built around opaque ownership, flag changes, falsified positions, ship-to-ship transfers and periods of “going dark” on automatic identification systems. The US has said its naval measures have halted economic trade to and from Iran by sea, but commercial tracking data and outside reporting suggest some Iran-linked vessels are still finding paths through or around the cordon. At least one broader estimate now puts the volume moved by the latest flotilla at roughly nine million barrels.

Pressure on shipping through Hormuz remains severe. Traffic through the strait has fallen dramatically from normal levels, with only a handful of ships managing to pass on some days against a pre-conflict daily average of about 140. The disruption has stranded hundreds of vessels and tens of thousands of seafarers, while leaving dozens of non-Iranian supertankers trapped with cargoes on board. That matters far beyond the Gulf because the waterway usually carries about a fifth of global oil and gas flows, making even a partial shutdown a direct threat to supply chains, freight costs and energy pricing.

Yet the market response has been more restrained than the scale of the disruption might imply. Traders appear to be weighing two competing realities: the physical danger to navigation is real, but the worst-case scenario of a prolonged, total stop to Gulf exports has not fully materialised. Some ships tied to neutral or non-combatant countries have crossed at intervals, and others have experimented with altered routes, changed registrations and carefully timed transits. For Iran, every successful sailing carries strategic value, showing buyers and intermediaries that crude can still move, even if at higher risk and cost.

Washington, for its part, has widened the contest well beyond the immediate blockade zone. US forces this week boarded the tanker Tifani in the Bay of Bengal, saying it was carrying Iranian crude, while other operations have targeted Iran-linked shipping in waters far from the Gulf. Legal and diplomatic questions hang over those actions, especially during a fragile ceasefire extension, but the operational message is unmistakable: vessels suspected of moving Iranian oil may face interception far from Iran’s coastline. That expands uncertainty for shipowners, insurers and charterers already grappling with war risk, crew safety and compliance exposure.

Iran’s answer has been to lean harder on the tactics that built its shadow trade in the first place. Ships have been observed switching off transponders, manipulating their apparent locations and travelling at night to reduce visibility. Some have sailed with murky ownership records or flags designed to obscure links to sanctioned entities. Others appear to have relied on Iran’s selective control over passage through Hormuz, where vessels seen as politically acceptable have at times been allowed through while others were turned back or left waiting. This blurred operating environment makes verification slower, enforcement harder and the line between commercial shipping and geopolitical contest increasingly thin.