Amid tensions with Iran, President Donald Trump said on Twitter he has given orders for the US Navy to "shoot down and destroy" any Iranian gunboats found to be harassing US ships.
A US Navy video last week showed small Iranian fast boats coming close to American warships as they operated in the northern Persian Gulf near Kuwait, with US Army Apache helicopters.
"I have instructed the United States Navy to shoot down and destroy any and all Iranian gunboats if they harass our ships at sea," Mr Trump tweeted.
I have instructed the United States Navy to shoot down and destroy any and all Iranian gunboats if they harass our ships at sea.
— Donald J. Trump (@realDonaldTrump) April 22, 2020
Mr Trump did not cite a specific event in his tweet, or provide details. The White House had no immediate comment.
The US Navy's Bahrain-based 5th Fleet referred questions about the tweet to the Pentagon, which did not immediately respond to a request for comment.
Mr Trump's tweet came after Iran's Revolutionary Guard said it had put the Islamic Republic's first military satellite into orbit.
The launched immediately raised concerns among experts on whether the technology used could help Iran develop intercontinental ballistic missiles.
On Sunday, the Revolutionary Guard acknowledged it had a tense encounter last week with US warships in the Persian Gulf, but alleged without offering evidence that American forces sparked the incident.
The Guard and the Navy routinely have tense encounters in the Persian Gulf and its narrow mouth, the Strait of Hormuz, through which 20% of all oil passes.