ABOARD THE USS WARRIOR — Telling the difference between a deadly surface mine and a bloated sheep carcass bobbing belly-up in the Persian Gulf is among the skills being tested by an international coalition of sailors and divers.

A 12-day mine-hunting exercise in Middle East waters that ends Thursday, is demonstrating how sonar, underwater drones, helicopter-towed acoustic devices, magnetized cables and divers would counter any move by Iran to interfere with oil exports from the region.

“We train to hunt, we train to sweep, we train to neutralize,” Lt. Cmdr. Scott Nietzel, commanding officer of the USS Warrior, said in an interview on board the vessel, one of three U.S. minesweepers in the exercise. “You have a geographic area you need to go through, and most of what’s there is not interesting, most of it is garbage,” before determining whether it’s a mine.

Iranian officials have periodically threatened to disrupt the Strait of Hormuz in response to U.S.-led economic sanctions on its nuclear program and Israel’s threat to launch a strike against it. About 20 percent of the world’s traded oil is shipped daily through the Strait, which is 21 miles wide at its narrowest point.

Iran, with an inventory of as many as 5,000 mines, could deploy acoustic and magnetic mines hundreds of feet underwater as well as floating mines that explode on contact, according to American officials aboard the USS Ponce, which is commanding the exercise.

More than 30 nations have joined in mine-clearing drills that have stretched from the Persian Gulf to the Gulf of Oman to the Gulf of Aden and Djibouti. Participating ships aren’t entering the Strait.

Still, the exercise is under constant watch by Iran’s Islamic Revolutionary Guards Corps, its commander said Tuesday, according to the state-run Fars News Agency. The elite naval force controlled by Iran’s religious leaders also said it conducted its own military exercise this week, firing four missiles simultaneously that hit a target at sea the size of a ship and sinking it, according to Fars.

Capt. Jon Rodgers, commander of the Ponce, said the allied exercise is prudent practice in “what-if” scenarios.

“There’s no secret that there’s always the threat of mining the Strait of Hormuz,” Rodgers said. “How does the world deal with it? The best way to deal with it is to bring all the talent of mine counter-measures together and let’s practice.”

This included bringing French and Japanese equipment on board to test and compare it, he said. “You want to practice and be proactive so we can clear those mines in a shorter period,” he said.

The Ponce has been hosting teams of divers from France and the Netherlands, and the Warrior had a Canadian team aboard.

The Ponce is outfitted with two Kingfish unmanned underwater vehicles. The prototypes made by Exelis Inc. based in McLean, Va., can descend to a depth of 984 feet (300 meters) for as long as eight hours gathering data later analyzed on the Ponce.

The Warrior is one of the last all-wooden ships in the U.S. Navy, mostly Douglas Fir overlayed with fiberglass to minimize the vessel’s electronic and acoustic signature.

“You see a lot of things floating by in the ocean, including dead sheep,” Nietzel said. “If you see a bloated, dead sheep carcass with its legs sticking up in the air from a ways – in the right light – it might look an awful lot like a floating mine,” he said.

“We’ve probably seen four or five sheep” since arriving on deployment in June, he said. Nietzel spoke as the Warrior was located about 80 miles from the Iranian coast and 280 miles north of the Strait of Hormuz.

Detecting a mine that can home in on a ship’s propeller noise or its metallic signature starts by assessing a “white blur” on the Warrior’s AN/SQQ-32 sonar made by Raytheon Co. based in Waltham, Mass., Mineman Senior Chief Felipe Gallegos said in an interview.

A determination is made whether the blur is a “mine-like” object that needs further examination by a diver or by the AN/SLQ-48 “mine neutralization” robot made by Alliant Techsystems Inc. based in Arlington, Va.

“If it’s 30 feet long, you know pretty much it’s a bus, but if it’s five feet by four feet, that’s pretty much a mine,” he said.

While the orange-colored robot can dive as deep as 2,000 feet, it usually operates from 200 feet to 500 feet. The robot has a video camera with a live link to the ship and a “bomblet” that can be laid on a mine and detonated once the robot leaves the area, said Mineman 2nd Class Andrew Taylor.

“We send out a code that talks to the bomblet out there and it blows up the bomblet and the mine,” Taylor said.

The robot also can be equipped with a remotely operated cutting device to snip a cable and float a mine to the surface.

The Warrior can sweep for mines over a large area by unraveling thick magnetic cables designed to simulate a large vessel and induce explosions safely, said Mineman Senior Chief Lawrence Stolinski.

“It’s about like mowing the grass in your yard — you go back and forth,” he said.

The Warrior and the seven other Avenger-class vessels in the region can be modified to carry the latest U.S. counter-mine system — the SeaFox, a one-shot underwater disposal drone guided by fiber optics that blows itself up to destroy a mine on command.

The SeaFox also can be carried by MH-53E mine-sweeping helicopters, 5th Fleet spokesman Lt. Greg Raelson said in an e-mail. The SeaFox was developed for Lockheed Martin Corp. based in Bethesda, Md., by a unit of Bremen, Germany-based Atlas Elektronik.

The MH-53E’s current mine-hunter gear includes acoustic and magnetic “sweeps,” devices lowered while the copter hovers and towed below the surface to detonate mines fooled by their signatures.

An acoustic sweep “simulates a ship’s prop,” said Naval Aircrewman (Helicopter) 2nd Class Leonard Johnson Jr. of Helicopter Mine Countermeasures Squadron 15, who lowered the device into the water from his MH-53E in a demonstration for reporters visiting the Ponce.

“So as we pull that through the water, if there is any mine that goes off an acoustics signal, the device that we are pulling” will detonate it, Johnson said.

“I really didn’t realize the importance” of the mission “until we came out here” and was made aware that “this percentage of the world’s oil comes through the Strait of Hormuz, so it’s a pretty big deal,” Johnson said.