Four Iranian Islamic Revolutionary Guard Corps Navy (IRGCN) vessels are seen next to the guided-missile destroyer USS Paul Hamilton in the Gulf, April 15, 2020. /Reu
"Armed vessels approaching within 100 meters of a U.S. naval vessel may be interpreted as a threat," according to the text of the notice. Otherwise, U.S. military vessels will take "lawful defensive measures" against the ships.
The usual actions taken in case of a close encounter involve turning the ship away from the approaching vessel, sounding a horn and shooting off flares before firing even warning shots. The strange warning follows U.S. President Donald Trump's threat last month to fire on any Iranian ships that harass Navy vessels.
A U.S. official, speaking on condition of anonymity, said the new notice to mariners was not a change in the U.S. military's rules of engagement.
However, some Russian experts believe that the U.S. Navy apparently signals it might be ready to take some more drastic measures if its latest warning is ignored.
The Bahrain-based U.S. Naval Forces Central Command said in a statement that its notice was "designed to enhance safety, minimize ambiguity and reduce the risk of miscalculation."
It follows an incident last month in which the Pentagon claimed 11 Iranian vessels conducted "dangerous and harassing" maneuvers near six U.S. ships. At one point, the Iranian vessels came within nine meters of a U.S. vessel, which the U.S. military called "dangerous and provocative."
Tehran dismissed the U.S. accusations as "false and fake stories," arguing that it was the U.S. that broke maritime regulations in the Persian Gulf. But Islamic Revolutionary Guard Corps (IRGC) commander Major-General Hossein Salami later ordered the nation's naval forces to destroy any American warship threatening the security of Iranian vessels.
The back-and-forth is just the latest example of razor-sharp tension between Washington and Tehran, which has steadily escalated since 2018, when Trump withdrew from Iran's 2015 nuclear deal with six world powers and reimposed crippling sanctions.