The US Navy held a joint drone drill with the United Kingdom on Friday in the Persian Gulf, testing the same unmanned surveillance ships that Iran twice has seized in recent months in the Middle East.
The exercise comes as the US Navy separately told commercial shippers in the wider Mideast that it would continue using drones in the region and warned against interfering with their operations.
The drone drill - and the American pledge to keep sailing them - also comes as tensions between the US and Iran on the seas remain high amid stalled negotiations over its tattered nuclear deal with world powers and as protests sweep the Islamic Republic.
Friday's drill involved two American and two British warships in the Persian Gulf, as well as three Saildrone Explorers, said Cmdr. Timothy Hawkins, a spokesman for the Navy's Mideast-based 5th Fleet.
The drones searched for a target on the seas, then sent the still images its cameras captured back to both the warships and the 5th Fleet's command center in the island kingdom of Bahrain. There, an artificial intelligence system worked through the photos.
The 5th Fleet launched its unmanned Task Force 59 last year. Drones used by the Navy include ultra-endurance aerial surveillance drones, surface ships like the Sea Hawk and the Sea Hunter and smaller underwater drones that resemble torpedoes.