The U.S. Navy issued a warning on Tuesday telling mariners in the Gulf to stay under 100 meters away from American warships, or risk being “interpreted as a threat and subject to lawful defensive measures," according to a report.
"Armed vessels approaching within 100 meters of a U.S. naval vessel may be interpreted as a threat and subject to lawful defensive measures," a text of the notice read, according to Reuters.
Last month, 11 Iranian vessels came close to U.S. Navy and Coast Guard ships in the Gulf, in what the U.S. military called “dangerous and provocative” activity. Iranian vessels came within 10 yards of the U.S. Coast Guard cutter Maui during the incident, the U.S. military said.
The Bahrain-based U.S. Naval Forces Central Command said the notice was issued "in order to enhance safety, minimize ambiguity, and reduce opportunities for miscalculation," citing recent events.
In recent years, Iranian vessels have been accused of harassing U.S. ships in the Persian Gulf and Strait of Hormuz, which sees 20 percent of the world’s oil pass through.
The notice to mariners was not a change in the U.S. military’s rules of engagement, a U.S. official said, according to Reuters.
It comes as the Pentagon previously stated that Trump’s threat to Iran -- made after the incident -- was meant to underscore the Navy’s right to self-defense.
Defensive measures have typically included turning a ship away from the approaching vessel, sounding its horn, shooting off flares, and ultimately firing warning shots to force the vessel away. But offering a specific distance is new for the Navy.
“Our ships are conducting routine operations in international waters wherever international law allows and do not seek conflict,” said Cmdr. Rebecca Rebarich, a Bahrain-based 5th Fleet spokeswoman. “However, our commanding officers retain the right to self-defense if deemed necessary.”
Tensions have mounted between Washington and Tehran since 2018 after Trump withdrew from Iran’s 2015 nuclear deal and imposed strict sanctions on the country.
On several occasions in 2016 and 2017, U.S. Navy ships fired warning shots at Iranian vessels when they got too close, the news organization reported.
The Associated Press contributed to this report