Close interactions with Iranian military vessels were not uncommon in 2016 and 2017. On several occasions, U.S. Navy ships fired warning shots at Iranian vessels when they got too close.
"I have instructed the United States Navy to shoot down and destroy any and all Iranian gunboats if they harass our ships at sea," Trump wrote in a tweet, hours after Iran's Revolutionary Guards Corps said it had launched the country's first military satellite into orbit.
The United States should focus on saving its military from the coronavirus, an Iranian armed forces spokesman said after Trump's comments.
While the Navy has the authority to act in self-defense, Trump's comments appeared to go further and are likely to stoke tensions between Iran and the United States.
Senior Pentagon officials said that Trump's comments on Iran were meant as a warning to Tehran, but suggested that the U.S. military would continue to abide by their existing right to self-defense instead of any changes to their rules.
"The president issued an important warning to the Iranians, what he was emphasizing is all of our ships retain the right of self-defense," Deputy Secretary of Defense David Norquist told reporters at the Pentagon.
Earlier this month, the U.S. military said 11 vessels from the IRGCN came close to U.S. Navy and Coast Guard ships in the Gulf, calling the moves "dangerous and provocative."
At one point, the Iranian vessels came within 10 yards (9 meters) of the U.S. Coast Guard cutter Maui.
While such interactions at sea had occurred occasionally a few years ago, they had stopped recently.
Tensions between Iran and the United States increased earlier this year after the United States killed Qassem Soleimani, the head of Iran’s elite Quds Force, in a drone strike in Iraq.
Iran retaliated on Jan. 8 with a rocket attack on Iraq’s Ain al-Asad base where U.S. forces were stationed. No U.S. troops were killed or faced immediate bodily injury, but more than 100 were later diagnosed with traumatic brain injury.Iran's Revolutionary Guards Corps said on Wednesday it had successfully launched the country's first military satellite into orbit.