Iran has blacklisted 45 tankers for violating its rules for crossing the Strait of Hormuz, warning that the vessels could face fines, detention, and cargo confiscation. The announcement, made via a post on X from the Persian Gulf Strait Authority (PGSA), a new body set up by Iran to manage the strait, escalates threats over the key waterway six months into the conflict.

The warning was issued within days of the U.S. threatening Iran with "the toughest sanctions in history," and Iran saying its response to any new U.S. threats would be "devastating," as reported by multiple outlets. 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 L&S), ADNOC's subsidiary Navig8 Tankers, and Saudi Arabia's national shipping carrier Bahri. Ships owned by Klaveness Ship Management, Stolt Tankers, and South Korea's Sinokor were also included, according to a report from The Economic Times.

The PGSA, which wrote in its X post that cargo owners should refer to an updated list of non-compliant vessels, also warned that any ships engaging in ship-to-ship transfers or transshipment with the named vessels would be added to the restricted list, as reported by several sources. The authority said ships seeking removal from the list must submit a request with explanations to Iran's maritime authorities.

Shipping companies that were named on the list have not immediately responded to Reuters' requests for comment, according to The Star and Al-Monitor.

Background and Context

The action comes amid a broader U.S.-Iranian standoff. The U.S. has threatened a new round of sanctions, with Treasury Secretary Scott Bessent warning of an "economic D-Day" against Tehran, and Iran has threatened a "devastating" response. The PGSA's move is widely seen as a response to those U.S. threats, with Crude Oil Prices Today framing it as "Tehran retaliating against Washington's looming ' economic D-Day.'"

The blacklisting follows -clashes over the waterway's supply routes. Before the conflict, the Gulf was estimated to provide about 20% of the world's daily crude oil and LNG, but traffic through Hormuz has since plummeted. A-Locations data from UK Maytime Information via Reuters suggests commercial traffic is now roughly 90% below pre-war levels. And Energy Secretary Chricht Chris Wright said on Friday that the seven-day average of oil leaving the strait was over 8 million barrels a day, but commercial trackers have reported lower volumes, highlighting a discrepancy.

Broader impact

The blacklist adds to the risks facing tanker operators and freight forwarders as they navigate the strategic clash between Washington and Tehran. The shipping industry is already dealing with the fact that few vessels are transiting the strait. As reported by several outlets including The Economic Time and Fooddata Centre, the list prompts affected charterers and shipowners to consider the future routes and liabilities.

The ships that have been blacklisted may face legal and operational consequences, ranging from monetary fines to the detention of vessels and seizure of cargo. And since the list includes smaller companies and possibly other influential players, insurers may also be affected, as they could be dealing with polluted risks.

Meanwhile, the U.S. and its allies – closely with U.S. energy department administration – have been working to keep oil flowing through the waterway, according to reports. The U.S. Navy has been helping to transport tankers quietly through the strait, a move that has helped restore some export volumes.

But the new blacklist may complicate those efforts, as tankers that are named – or that have touched the named ships – may be considered non-compliant by Tehran, and could face further restrictions. The exact rules that the tankers are accused of violating have not been specified by Iran. Gal Hasni, a former head of the U.S. National Security Council's Gulf affairs, said in the U.S. context that the new gregarious tactics are unusual.