Confrontation comes amid talks in Vienna between Iran and major powers on the mechanics of a US return to a landmark 2015 nuclear deal abandoned by then-president Donald Trump.
An American warship fired warning shots when vessels of Iran's paramilitary Revolutionary Guard came too close to a patrol in the Persian Gulf, the US Navy has said.
The Navy released black-and-white footage of the encounter Monday night in international waters of the northern reaches of the Persian Gulf. In it, lights can be seen in the distance and what appears to be a single gunshot can be heard, with a tracer round racing across the top of the water.
Iran did not immediately acknowledge the incident.
The Navy said the USS Firebolt fired the warning shots after three fast-attack Guard vessels came within 68 yards (62 meters) of it and the US Coast Guard patrol boat USCGC Baranoff.
“The US crews issued multiple warnings via bridge-to-bridge radio and loud-hailer devices, but the (Guard) vessels continued their close-range maneuvers,” said Cmdr. Rebecca Rebarich, a spokeswoman for the Mideast-based 5th Fleet.
“The crew of Firebolt then fired warning shots, and the (Guard) vessels moved away to a safe distance from the US vessels.”
She called on the Guard to “operate with due regard for the safety of all vessels as required by international law.”
“US naval forces continue to remain vigilant and are trained to act in a professional manner, while our commanding officers retain the inherent right to act in self-defence,” she said.
US Navy patrol ship fires warning shots at three Iranian military boats in the Gulf Sea in a worrying escalation in tensions pic.twitter.com/cytiMsWI3R— TRT World Now (@TRTWorldNow) April 28, 2021
'Unsafe and unprofessional'
The incident on Monday marked the second time the Navy accused the Guard of operating in an “unsafe and unprofessional” manner this month alone after tense encounters between the forces had dropped in recent years.
Footage released Tuesday by the Navy showed a ship commanded by the Guard cut in front of the USCGC Monomoy, causing the Coast Guard vessel to come to an abrupt stop with its engine smoking on April 2.
The Guard also did the same with another Coast Guard vessel, the USCGC Wrangell, Rebarich said. Such close passes risk collisions.
The interaction marked the first “unsafe and unprofessional” incident involving the Iranians since April 15, 2020, Rebarich said.
In 2017, the Navy recorded 14 instances of what it describes as “unsafe and or unprofessional” interactions with Iranian forces. It recorded 35 in 2016, and 23 in 2015.
The incidents at sea almost always involve the Revolutionary Guard, which reports only to Supreme Leader Ayatollah Ali Khamenei.
Some analysts believe the incidents are meant in part to squeeze President Hassan Rouhani’s administration after the 2015 nuclear deal. They include a 2016 incident in which Iranian forces captured and held overnight 10 US sailors who strayed into the Islamic Republic’s territorial waters.
The incident comes as Iran negotiates with world powers in Vienna over Tehran and Washington returning to the 2015 nuclear deal.
In offering to rejoin the agreement in February, US President Joe Biden stressed the need to reduce "Iran's destabilizing activities across the Middle East."
It also follows a series of incidents across the Mideast attributed to a shadow war between Iran and Israel, which includes attacks on regional shipping and sabotage at Iran’s Natanz nuclear facility.