US President Donald Trump wrote on Truth Social on Wednesday that the strikes on Iran were a response to attacks on ships, and that if Iran carried out further attacks "the situation will get worse!"
He added that US strikes would intensify if Iran did not halt its attacks.
On a separate matter, the US president said he would ask the Supreme Court to reconsider the case related to birthright citizenship.
The Supreme Court last month rejected Trump's attempt to impose restrictions on birthright citizenship in the United States.
The US president arrived late on Wednesday in Britain at RAF Mildenhall on his way back to the United States following the NATO summit in Turkey.