In Washington, a US defense official, speaking on condition of anonymity, cast doubt on any claims that the Iranian ships were approaching US maritime borders. But the official added that "ships are free to operate in international waters."
The United States and its allies regularly stage naval exercises in the Gulf, saying they want to ensure freedom of navigation in the waterway through which 40 percent of the world's seaborne oil exports passes.
The unofficial comments come in response to a report claiming a number of Iranian warships had been ordered to approach US maritime borders as a response to the stationing of US vessels in the Gulf, the semi-official Fars news agency reported on Saturday.