American and Iranian warships were involved in a tense encounter in the Persian Gulf earlier this month in the first such incident for about a year amid turmoil over Tehran’s tattered nuclear deal, the US Navy has reported.

Footage released by the Navy showed a ship commanded by Iran’s paramilitary Revolutionary Guard cut in front of the USCGC Monomoy on April 2, causing the Coast Guard vessel to come to an abrupt stop with its engine smoking.

The Guard also did the same with another Coast Guard vessel, the USCGC Wrangell, said Commodore Rebecca Rebarich, a spokeswoman for the Navy’s Mideast-based 5th Fleet.

Iran did not immediately acknowledge the incident, which resulted in no injuries or damage.

“The US crews issued multiple warnings via bridge-to-bridge radio, five short blasts from the ships’ horns, and while the (Iranian) Harth 55 responded to the bridge-to-bridge radio queries, they continued the unsafe manoeuvres,” Ms Rebarich said.

“After approximately three hours of the US issuing warning and conducting defensive manoeuvres, the (Iranian) vessels manoeuvred away from the US ships and opened distance between them.”

The interaction marked the first “unsafe and unprofessional” incident involving the Iranians since April 15, 2020, Ms Rebarich said. However, Iran had largely stopped such incidents in 2018 and nearly in the entirety of 2019, she said.

In 2017, the Navy recorded 14 instances of what it describes as “unsafe and or unprofessional” interactions with Iranians 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 put pressure on moderate 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. It also follows a series of incidents across the Middle East attributed to a shadow war between Iran and Israel, which includes attacks on regional shipping and sabotage at Iran’s Natanz nuclear facility.