Iran said it had blacklisted 45 tankers that had broken its rules for crossing the Strait of Hormuz, and would take action against any vessels transferring loads with them, escalating its threats over the key waterway six months into the war.

The named vessels could be fined, detained and have their cargoes confiscated, according to an X post late on Sunday from the Persian Gulf Strait Authority, a new body set up by Iran to manage the strait.

The warning was issued within days of the US threatening Iran with “the toughest sanctions in history”, and Iran saying its response to any new US threats would be “devastating”.

The restricted list includes very large crude carriers, liquefied natural gas and liquefied petroleum gas tankers, and clean product vessels, among others.

Some of the named ships are owned by the United Arab Emirates’ ADNOC Logistics and Shipping, ADNOC’s subsidiary Navig8 Tankers, and Saudi Arabia’s national shipping carrier Bahri.

Any vessels involved in ship-to-ship transfers with the named vessels could be added to the blacklist, the Iranian X post added.

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The post did not spell out what it meant by Iran’s rules, but Tehran has in the past said shipowners should get its clearance to transit the strait and said ships should pay for security and other services.

The US has also imposed a naval blockade against Iran-related shipping.

The Gulf supplied about 20% of the world’s daily crude oil and liquefied natural gas before the Iran conflict disrupted tanker traffic.

US-coordinated efforts to shuttle tankers quietly through the Strait of Hormuz to fill supertankers waiting just outside it are helping restore some of those export volumes.

US Secretary of Energy Chris Wright said on X on Friday that the “7-day average of oil leaving the Strait is over 8 million barrels a day. Make no mistake, thanks to the US Navy, oil is flowing through the Strait of Hormuz.”

Ships owned by Klaveness Ship Management, Stolt Tankers and South Korea’s Sinokor were also included on the blacklist.

ADNOC declined to comment, while other shipping firms did not immediately respond to Reuters’ requests for comment.

The Persian Gulf Strait Authority has said cargo owners should refer to an updated list of vessels deemed non-compliant for voyages relating to the Gulf.

Ships seeking the removal of their names from the non-compliant vessels’ list must submit a request with relevant explanations to Iran’s maritime authorities, the post said.