The USS Abraham Lincoln aircraft carrier has entered CENTCOM waters in the Indian Ocean amid increasing threats from Iran, a senior U.S. official told Fox News on Monday.

Reports say Iran's Ayatollah Ali Khamenei has gone underground, suggesting the country may be preparing for military action. A leading U.S. drone expert told Fox on Sunday that Iran's drone swarms would pose a credible and serious threat to the Lincoln and its strike group.

The top U.S. official said the Lincoln was not yet ready for any possible future strikes against Iran.

Cameron Chell, CEO and co-founder of Draganfly, told Fox that Iran has created "an effective asymmetric threat against highly sophisticated military systems" with its fleet of unmanned drones, pairing "low-cost warheads with inexpensive delivery platforms."

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Chell said Iran can launch large numbers of relatively unsophisticated drones directly at naval vessels, creating saturation attacks that could overwhelm traditional defenses.

"If hundreds are launched in a short period of time, some are almost certain to get through," Chell said.

"Modern defense systems were not originally designed to counter that kind of saturation attack. For U.S. surface vessels operating near Iran, warships are prime targets," he added.

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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.

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," he said.

Fox News' Jennifer Griffin and Emma Bussey contributed to this report.