The move tightens the squeeze on Iranian oil sales after the US reimposed its blockade of Iranian ports on July 14 following the breakdown of a memorandum of understanding between Tehran and Washington to end the war.
Iran has only about 20 million barrels of crude oil left on vessels outside the blockade, off Singapore, Malaysia and China, the Treasury official said. The world uses about 100 million barrels of oil per day.
A second Treasury official said Iran has stopped loading and offloading crude oil vessels due to the blockade and sanctions.
President Donald Trump said on social media on Thursday that the US is having “productive discussions” with Iran over the war that began on February 28. Trump said the US will not attack Iran before the midterm elections on November 3.
Vessels targeted by the US sanctions include the Comoros-flagged Paritosh, the Panama-flagged Bitu and the Bahamas-flagged Gas Lucky.
(Reporting by Timothy Gardner and Daphne Psaledakis; Editing by Michelle Nichols, Nia Williams and Paul Simao)
