"I have instructed the United States Navy to shoot down and destroy any Iranian gunboats if they harass our ships at sea," US President Donald Trump tweeted.
Relations between the US and Iran deteriorated in May 2019, when the US imposed sanctions targeting Iran's oil exports. In response, Iran began a counter-pressure campaign.
The encounter happened last week. Six US Navy warships were conducting drills with US army Apache attack helicopters in international waters off Iran last Wednesday when they were repeatedly harassed by 11 Iranian Islamic Revolutionary Guard Navy vessels, the US Navy's 5th Fleet reported.
The Iranian ships repeatedly crossed in front and behind the U.S. vessels at extremely close range and high speeds, including multiple crossings of one ship, the Puller, with a 50-yard nearest point of approach and within 10 yards of another boat, the Maui's, bow, a 5th Fleet statement said.