The United States has deployed a fleet of robot subs in the Gulf to prevent Iran from blocking the strategic Strait of Hormuz with mines in the event of a crisis, officials say.
The SeaFox drone "has been deployed in the Fifth fleet AOR", which includes the Persian Gulf and the Arabian Sea, a Navy official told AFP, confirming information first reported in the Los Angeles Times newspaper.
The undersea drone, about 1.2 metres long and equipped with a camera and sonar, is guided by a cable from a ship.
German manufacturer Atlas Electronik says the drone has a range of about 1000 metres and carries an explosive to destroy mines.
"SeaFox devices will be employed from MCMs," or mine counter-measure ships, in the Persian Gulf, the Navy official said.
Fears of a closure of the Strait of Hormuz - through which about a fifth of the world's traded oil passes - intensified earlier this year after Iran threatened to close it if Western governments kept up efforts to rein in Tehran's controversial nuclear program by choking off its oil exports.
In response, the US military has been bolstering its presence in the region.
It sent four minesweeper ships in early June, joining four other minesweeping vessels in the region, according to the Fifth Fleet.
The Navy also has MH-53 Sea Stallion helicopters and USS Ponce, an old amphibious warship that has been converted into a "floating base", stationed in Bahrain, home to the Fifth Fleet headquarters.
And in late April, a squadron of F-22 stealth fighters was sent to the Al Dhaafra Air Base in the United Arab Emirates.
Iran has an arsenal of about 2000 sea mines that can be laid by any one of its dozen submarines or its many speedboats.