He said the USS Boxer downed the drone over the Strait of Hormuz - a strategic sea passage in the Gulf - after it came within 1,000 yards (914m) of the ship.

Iran said it had no information about losing a drone. In June, Iran shot down a US military drone in the area.

Iran has been blamed by the US for attacks on tankers which have happened in the world's key shipping area since May. Tehran denies all the accusations.

The recent incidents have triggered fears of a military conflict in the region.

Speaking at the White House, Mr Trump said: "I want to apprise everyone of an incident in the Strait of Hormuz today involving USS Boxer, a navy amphibious assault ship.

"The Boxer took defensive action against an Iranian drone which had closed into a very, very near distance, approximately 1,000 yards (914m), ignoring multiple calls to stand down and was threatening the safety of the ship and the ship's crew. The drone was immediately destroyed.

"This is the latest of many provocative and hostile actions by Iran against vessels operating in international waters. The United States reserves the right to defend our personnel, facilities and interests."

A defence department official quoted by the New York Times said the drone had been brought down using electronic jamming equipment.

Meanwhile, a senior Iranian official dismissed the US statement. In an English tweet posted on 19 July, Deputy Foreign Minister Abbas Araqchi even suggested the US may have downed its own drone by mistake.