U.S. military assets headed to the Middle East could face a serious threat from Iranian drone swarms as reports emerge that Iran’s supreme leader has gone underground, according to a leading military drone expert.

Cameron Chell, CEO and co-founder ofU.S. surface vessels operating near Iran, warships are prime targets."

The warning comes as a senior U.S. official confirmed to Fox News Digital that the USS Abraham Lincoln aircraft carrier strike group had not yet crossed into U.S. Central Command’s area of responsibility in the Indian Ocean.

"It is close, but technically not in CENTCOM yet," the source said. This would indicate the carrier strike group is not yet in a position to strike Iran.

U.S. officials say Washington is reinforcing its military posture in response to growing instability inside Iran, boosting its presence by air, land and sea, while closely monitoring developments in Syria.

A squadron of F-15 fighter jets has deployed to the region, and C-17 aircraft carrying heavy equipment have arrived.

Once the aircraft carrier strike group enters the CENTCOM area of operations, which should be soon, it will still take several days before the strike is fully on station.

Chell noted that U.S. and allied militaries are rapidly developing defenses but uncertainty over new capabilities on the USS Abraham Lincoln carrier groups for managing multiple Iranian drones flying in formation remains.  He emphasized that Iran’s drone fleet is a concern.

"These drones give Iran a very credible way to threaten surface vessels," he said. "U.S. assets in the region are large, slow-moving and easily identifiable on radar, which makes them targetable."

"Iran’s strength lies instead in these low-cost, high-volume drone systems—particularly one-way strike drones designed to fly into a target and detonate."

Chell explained that Iran gained an early advantage in what are known as Category One and Category Two drone systems—low-cost platforms that can be produced in large numbers and used effectively in asymmetric warfare.

"Category Three systems are a completely different matter," he said. "In that area, Iran is decades behind the United States."

The U.S. military buildup coincides with widespread unrest inside Iran. Protests erupted Dec. 28 amid mounting public discontent.

The Donald Trump also addressed the deployment on Jan. 21, telling reporters, "We have a big flotilla going in that direction, and we’ll see what happens. We have a big force going towards Iran. I’d rather not see anything happen, but we’re watching them very closely."