A US coast guard ship fired about 30 warning shots as a group of 13 Iranian fast boats sped toward US navy vessels in the strait of Hormuz, in what the Pentagon called “unsafe and unprofessional” maneuvers by the naval arm of the Islamic Revolutionary Guard Corps (IRGCN). The incident marked the second time within the last month that US military vessels have had to fire warning shots because of what they said was unsafe behavior by Iranian vessels in the region, after a relative lull in such interactions over the past year. John Kirby, a Pentagon spokesperson, said the warning shots were fired after the Iranian fast boats came as close as 150 yards (450ft) of six US military vessels, including the USS Monterey, that were escorting the guided-missile submarine Georgia. The US coast guard cutter Maui fired the warning shots from a .50-caliber machine gun before the Iranian vessels left, Kirby said. “It’s significant … and they were acting very aggressively,” he said, adding that the number of Iranian vessels was more than in the recent past. “After the second round of warning shots the 13 fast attack craft from the IRGC-N broke contact,” he said, ending the encounter. A day earlier, the Monterey had intercepted an arms shipment aboard a dhow in the Arabian Sea apparently headed for Yemen, whose Houthi rebels are supported by Iran. In April, a US military ship fired warning shots after three vessels from IRGCN came close to it and another American patrol boat in the Gulf. “Sadly harassment by the IRGCN is not a new phenomenon,” said Kirby “It’s unsafe, it’s unprofessional. It’s the kind of activity that can lead to somebody getting hurt, and can lead to a real miscalculation there in the region,” he said. “That doesn’t serve anybody’s interests,” Kirby said. The latest incident comes as world powers and Iran seek to speed up efforts to bring Washington and Tehran back into compliance with the 2015 nuclear accord. US officials returned to Vienna last week for a fourth round of indirect talks with Iran on how to resume compliance with the deal, which Donald Trump abandoned in 2018, prompting Iran to begin violating its terms about a year later.