U.S. officials said the Navy sent the SeaFox submersible to the region to search for and destroy mines in the Persian Gulf, the Los Angeles Times reported. U.S. Marines Gen. James Mattis, the top U.S. military commander in the Middle East, issued an urgent order for the submersible in May.
The Times reports authorities in the United States are worried Iran may respond to sanctions by targeting oil installations in the Persian Gulf.
Iranian Rear Adm. Mahmoud Fahimi, deputy commander of the Islamic Revolutionary Guards Corps, said U.S. efforts at demining were fruitless.
"Americans talk a lot about different things but in practice they are faced with problems," he was quoted by Iran's state-funded broadcaster Press TV as saying. "We have no doubt that the United States can't do anything in the minesweeping sphere."
U.S. Defense Secretary Leon Panetta said the Iranians need to understand the consequences of disrupting regional shipping lanes.
"The United States is fully prepared for all contingencies here," he said in a statement.