US Naval Blockade Hammers Iran Oil Exports, Forces Floating Storage Maritime Activity Reports, Inc. By Nerijus Adomaitis and Ahmad Ghaddar May 1, 2026 U.S. Marines from the 31st Marine Expeditionary Unit depart USS Tripoli (LHA 7) to board M/V Blue Star III, a commercial ship suspected of attempting to transit to Iran in violation of the U.S. blockade of Iranian ports, April 28, 2026. U.S. forces released the vessel after conducting a search and confirming the ship’s voyage would not include an Iranian port call. (U.S. Marine Corps photo) A U.S. naval blockade of Iranian ports has shrunk Tehran's oil exports, stranding a growing stockpile of crude on tankers as Iranian storage sites run out of space, shipping data showed and analysts said. With some vessels switching off tracking systems and U.S. forces turning back Iranian tankers, how much crude Iran is delivering to customers, particularly main customer China, is impossible to measure. Just a handful of carriers carrying Iranian crude have left the Gulf of Oman between April 13-25, oil analytics firm Vortexa said. That's down over 80% from a comparable period in March, when Iran exported 23.4 million barrels, LSEG data shows. Some of Tehran's vessels have been intercepted by the U.S. after leaving Iranian ports, along with sanctioned container ships and Iranian tankers in Asian waters. "At this stage, we estimate that around 4 million barrels of Iranian crude has successfully moved out of the Gulf of Oman. We are not currently able to confirm whether any of those vessels have since been interdicted," it said in an email to Reuters. The loss of Iranian supply adds to wider market tightness as the war has effectively closed the Strait of Hormuz, curtailing oil exports from Saudi Arabia, the UAE, Kuwait and Iraq and sending prices higher, something the U.S. has sought to avoid. Last month, the U.S. granted Tehran an unexpected temporary sanctions waiver on energy exports to allow prices to cool. Benchmark Brent crud