US worries Kim Jong Un will 'miscalculate' chances against US, South Korea "Our biggest concern is that he's going to miscalculate."

 -- A top-ranking U.S. military official on the Korean peninsula said the biggest concern is that North Korean leader Kim Jong Un will "miscalculate" his chances of winning any military fight against the U.S. and its ally, South Korea.

“Our biggest concern is that he's going to miscalculate. That's always our concern,” Lt. Gen. Thomas W. Bergeson, the number two U.S. military officer in South Korea told ABC News’ Martha Raddatz on "This Week" Sunday.

“We want to make it crystal clear to the North Koreans' leadership that this would be a completely futile endeavor were he to challenge this strong, ironclad bilateral alliance,” Bergeson said in an interview at the U.S. Osan Air Base in South Korea, where ABC News got exclusive access to the base's air operations center.

Osan Air Base is just 48 miles from the border with North Korea, and its air operations center tracks airspace over all of South Korea. The center is first to detect whenever North Korea launches a missile.

In recent months, North Korea has conducted several ballistic-missile tests -– five in 2017, including a failed launch Saturday.

Raddatz asked U.S. military leaders in the south how the air operations center responds when North Korea shoots off a ballistic missile.

“You think it would be hectic but due to the level of training of the soldiers here, it's actually a calm exercise. I would compare it to maybe an air traffic controller tower ... when we're in exercise or even real world when we ramp up for crisis,” Col. Mark Holler, commander, 35th Air Defense Artillery, said.

Kim Jong Un has warned that North Korea is prepared to strike and take out American military bases, but Bergeson is confident the reclusive regime would not succeed.

“They could try, but as you saw today out here [our] air defense artillery brigade ... [has] the technology and capability and they're ready to intercept those kinds of missiles. so they could try but it'll be futile,” he said.

The U.S. air base’s biggest tool in defense is the patriot missile, designed to detect and stop a wide range of attacks -- including from inbound ballistic missiles -- with nearly 100 percent accuracy, the military claims.

But while military leaders on the base say they are prepared for any attack that could come their way, all-out war with North Korea would be the worst possible outcome, said Col. Andrew Hansen, commander of the 51st Fighter Wing at Osan Air Base.

“It would be a mess. War is always -- war is hell. It would be very brutal,” said Col. Andrew Hansen, commander of the 51st Fighter Wing at Osan Air Base. “I mean we have a very credible adversary.”