Donald Trump has instructed the US Navy to shoot down and destroy Iranian gunboats "if they harass our ships at sea".
A U.S. 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 U.S. Army Apache helicopters.
On Sunday, Iran's Revolutionary Guard acknowledged it had a tense encounter with U.S. warships in the Persian Gulf, but alleged without offering evidence that American forces sparked the incident.
Writing on Twitter on Wednesday, the US president wrote: "I have instructed the United States Navy to shoot down and destroy any and all Iranian gunboats if they harass our ships at sea."
It comes as Iran's Revolutionary Guard said it put the Islamic Republic's first military satellite into orbit, dramatically unveiling what experts described as a secret space program with a surprise launch on Wednesday.
Iran appears to have abandoned the limitations of its nuclear deal with world powers that President Donald Trump unilaterally withdrew America from in 2018.
President Trump's decision set off a months long series of escalating attacks that culminated in a U.S. drone strike in January that killed a top Iranian general in Iraq, followed by Tehran launching ballistic missiles at American soldiers in Iraq.
