WASHINGTON — President Trump said on Wednesday that he has told the Navy to shoot down and destroy any Iranian fast boats that harass American naval ships, in what would be a sharp escalation of the risky maneuvers performed by the two adversaries in the Persian Gulf and the Arabian Sea.
The president’s abrupt statement, which he announced on Twitter, came a full week after the Pentagon accused Iran of sending 11 fast boats to conduct “dangerous and harassing approaches” to six American warships in the Persian Gulf.
The Iranian vessels, according to the Defense Department, “repeatedly crossed the bows and sterns” of the American ships at high speed, coming within 10 yards of one ship.
Mr. Trump did not say anything when the episode took place last week; such maneuvers have occurred for years, as American warships ply the Persian Gulf near Iranian territorial waters and Iran shows its ire by sending fast boats to harass the ships. Usually, the incidents end with warnings from the Pentagon.
But Mr. Trump on Wednesday suddenly escalated the threatened American response, in a tweet that seemed to catch the Pentagon by surprise. “I have instructed the United States Navy to shoot down and destroy any and all Iranian gunboats if they harass our ships at sea,” he wrote on Twitter.
The Navy referred all questions to the White House. A Defense Department official said that the service had not received any formal policy directive from Mr. Trump ordering the Navy to start shooting Iranian gunboats. A U.S. military official said that there have been no further incidents with the Iranians, fast boats or otherwise, since the one last week.
The president has a history of Twitter announcements that seem at odds with traditional policy, including that involving the military and its rules and operations.
American military units on the ground and at sea abide by strict rules on “escalation of force,” a ladder that includes audible warnings, flares and maneuvers before a shot is fired, often as a last measure.
Mr. Trump’s directive, in many ways, discounts this entire process and could lead to injury and death on an already crowded, and often confusing, waterway such as the Persian Gulf.
The Navy released video of last week’s incident, which showed fast boats zooming close to an American warship. “He’s taking a bow,” one American voice is overheard saying, as one Iranian boat circles the ship.
Tensions between the United States and Iran have been high for more than a year, and the coronavirus crisis has not ushered in any easing.
The Trump administration has continued to impose its “maximum pressure” campaign of economic sanctions against Tehran after the United States withdrew from an international nuclear agreement; Tehran for its part has launched proxy attacks against American troops, interests and allies in the region.
Iran’s Islamic Revolutionary Guards Corps, which commands the fast boats, is a paramilitary organization, separate from Iran’s conventional military. The Revolutionary Guard Corps carry out operations across the Middle East, train Arab Shiite militias and oversee businesses in Iran.
In January, American drones killed Qassim Suleimani, a top Iranian general who headed the Quds Force, an elite unit of the Revolutionary Guards, drastically escalating tensions between Washington and Tehran.
Thomas Gibbons-Neff contributed reporting.