Iran has published a map claiming regulatory control over a stretch of the Strait of Hormuz that extends deep into the territorial waters of the United Arab Emirates and Oman, prompting five Gulf states to formally warn shipping companies through the International Maritime Organisation (IMO) not to comply.

In a post on X on Wednesday, Iran's Persian Gulf Strait Authority defined its claimed management zone as running from Kuh-e Mobarak in Iran to the south of Fujairah in the UAE at the strait's eastern entrance, and from the end of Qeshm Island in Iran to Umm al-Quwain in the UAE at its western entrance, The Caspian Post reports, citing Euronews.

The zone covers waters that the UAE and Oman regard as their own sovereign territory. All vessels transiting the defined area are required to obtain prior authorisation from the PGSA.

Bahrain, Kuwait, Qatar, Saudi Arabia and the UAE sent a joint letter to the IMO this week, warning commercial and merchant vessels not to engage with the PGSA or transit the waterway using Iran's designated route. The letter was distributed by the IMO.

Earlier in May, Iran had established an email-based application process for vessels seeking to transit the strait through the PGSA. The authority was said to have become operational on Monday.

The crucial waterway has been largely blocked since the outbreak of the Iran war on 28 February, first by Tehran, and then by a US blockade of Iranian ports and ships declared by President Donald Trump.

So far, the only operators paying PGSA tolls are predominantly Chinese-linked shadow fleet vessels. No Western-flagged operator has publicly acknowledged making a payment, partly because doing so could expose companies to US sanctions.

Tehran Keeps Pushing the Boundaries

The Washington-based think-tank Institute for the Study of War (ISW) said Iranian officials remained divided over nuclear concessions but had united around formalising control of the strait.

"Iran’s demands over the Strait of Hormuz demonstrate that Iranian officials believe they won the war because formalising Iranian control over the Strait of Hormuz is a territorial claim on the sovereign territory of another country," the ISW said in an assessment on Friday.

The institute noted that a new map published on Wednesday appeared to extend Iran's claimed management zone beyond the boundaries it had outlined on 4 May, suggesting a deliberate step-by-step expansion of its territorial claims.

"The new PGSA-defined zone runs from Kuh Mobarak in Iran to southern Fujairah in the United Arab Emirates (UAE) in the east and from the end of Gheshm Island in Iran to Umm al Qaiwain in the UAE in the west," the ISW explained.

"This change lays explicit claim to control over the territorial waters of the UAE and Oman," it concluded.

The UAE port of Fujairah sits at the seaward end of the Abu Dhabi National Oil Company's West-East pipeline, which was built specifically to allow oil exports to bypass the Strait of Hormuz.

Iran is also using the ceasefire period to rebuild its drone and missile programmes.

US intelligence officials said in May that Iran had resumed drone production ahead of schedule.

Disrupting Iran's drone programme is harder than targeting its ballistic missile infrastructure: drones rely on simpler, widely available components, while ballistic missiles require large specialised facilities and equipment.

China and Russia have, according to US officials cited by multiple outlets, been providing assistance with Tehran's rebuilding efforts, although the specific nature of that support has not been publicly confirmed.

Iran has not yet responded to Washington's latest proposal on the nuclear file, according to ISW. The two sides remain divided on the removal of Iran's enriched uranium stockpiles and the long-term status of the strait.