Maritime traffic through the critical Strait of Hormuz has fallen steeply this week, with the number of tankers and cargo ships plummeting by half, following a series of tit-for-tat strikes between the United States and Iran. According to maritime intelligence firm Kpler, just 23 tankers and cargo ships crossed the vital Gulf waterway on Wednesday, a sharp decline from 47 vessels recorded a week prior.
The Strait of Hormuz is a crucial passage through which more than a fifth of the world’s oil and gas supplies, along with fertiliser shipments and other vital goods, flow. For decades, vessels have been granted free passage through the strait. However, before the current conflict escalated, an average of 138 ships crossed daily, as reported by the Joint Maritime Information Center (JMIC), a multinational maritime group that includes the US.
The current downturn in traffic follows an attack on three tankers earlier this week, all of which were using a US-recommended route through Omani waters. These ships included a Qatar-owned liquefied natural gas (LNG) tanker, a Saudi-owned crude oil tanker, and a Liberia-flagged crude tanker. Kpler data indicates that after these incidents, the number of vessels using the Omani route has effectively ground to a halt.
This week’s attacks are part of a broader escalation. On February 28, after the US and Israel launched their first strikes on Iran, traffic through the strait initially fell to just a handful of ships per day. Iran responded by effectively closing the strait through ship attacks and mine-laying, prompting the US to impose a blockade on all shipping to and from Iranian ports.
The dispute over navigation routes has intensified, with Iran repeatedly asserting that the only “safe” passage is through its own waters. Iran’s top military command, Khatam al-Anbiya Central Headquarters, reiterated after this week’s strikes, “The only safe route for the passage of commercial ships and oil tankers in the strait is the route determined by the Islamic Republic of Iran.” The US, its Gulf allies, and governments in Europe and Asia oppose this stance, insisting that passage must remain free and open as it was before the conflict.
Despite a memorandum of understanding (MOU) signed between Iran and the US on June 17, which committed Tehran to “its best efforts for the safe passage of commercial vessels with no charge for 60 days,” tensions have flared. The MOU also stipulated that Iran would “conduct dialogue with the Sultanate of Oman to define the future administration and maritime services in the Strait of Hormuz.” Following this agreement, overall traffic levels in the strait did initially increase, peaking at 72 ships on June 24, with the Omani route seeing a peak of 28 vessels on June 25.
However, on June 25 and 27, two ships in Omani waters were struck, leading Iran to warn all vessels to use only its approved routes. US President Donald Trump accused Iran of a “foolish violation” of its truce, and the US military conducted strikes on Iranian targets. Speaking at the Nato summit on Wednesday, President Trump declared the memorandum of understanding “over,” though he noted negotiations between Iran and the US could continue.
Iran, in turn, has accused Washington of violating the agreement after the US Treasury revoked a license that had temporarily eased sanctions on Iranian oil exports. Iran’s Revolutionary Guard Corps further issued a statement through an affiliated news agency, asserting that “foreign powers have no claim to this land or to the Strait of Hormuz” and warning that “any interference in determining shipping routes” would “provoke a crushing response” and “seriously disrupt the gradual reopening process.”
Concerns about sea mines laid by Iran in internationally recognised shipping lanes, used before the conflict, have also contributed to holding traffic back from pre-war levels. Martin Kelly, a senior intelligence analyst at security firm EOS Risk Group, anticipates a familiar pattern: “There will now be a bit of back and forth between the US and Iran before they make friends again, shipping will peak and trough cautiously until Iran attacks another ship and the cycle starts again.” Jennifer Parker, a maritime security expert at the University of New South Wales, commented on the MOU’s vagueness, stating that “even on a generous reading, it does not permit Iran to attack civilian shipping in Omani waters.” She added, “Neither the promise of economic relief nor the threat of military punishment has, so far, changed Iran’s behaviour. The challenge remains finding the right balance between the carrot and the stick.”
