The Pentagon has said that an Iranian military helicopter came as close as 25 yards to USS Essex Navy ship in the Gulf of Oman, in a “reckless” move last week.

Iran’s Islamic revolution Guard Corp has released a video on November 13 showing the flight of the helicopter very close to the US Navy vessel. They said the incident took place on November 11.

Pentagon spokesman John Kirby was pressed by reporters during his briefing on Monday about why the Essex did not take any defensive measure. Kirby refused to elaborate saying that he would not comment on engagement rules enforced by Navy commanders in charge.

"The ship's commander did what he believed was in the best interest of the ship and its crew. They have necessary means to protect themselves," Kirby maintained.

Iranian forces have harassed US forces on many occasions before in the Persian Gulf region but the Essex incident in one of the closest approaches they have made to a US vessel.

Earlier last week the US military announced that USS Essex amphibious assault warship and a Marine expeditionary force had joined the Fifth Fleet in the Sea of Oman and had conducted exercises with the British Navy.