Iranian President Hassan Rohani has again threatened to close a key passageway for oil trade if the U.S. blocks oil exports.
The Strait of Hormuz is the waterway for nearly a third of all oil traded by sea.
Rohani has threatened to close the sea lane several times before, but he is yet to follow up on those threats.
The Trump administration restored sanctions on Iran's energy industry to try and pressure Tehran to give up its nuclear and missile tests.