During his meeting with nuclear scientists and engineers, Kim Jong-un complimented them for developing “nuclear warheads proficiently designed to create rapid nuclear reaction.”

“Preemptive nuclear attacks are not something monopolized by the U.S., if the U.S. attempts to hit or threaten our survival and autonomy with nuclear weapons, we will not hesitate to strike them first,” he was quoted as saying by the Korean Central News Agency. “This is true nuclear deterrence.”

Kim has been stepping up rhetoric against South Korea and the U.S. after the U.N. Security Council passed sanctions against it last week. Several countries including Seoul and Washington have also levied unilateral sanctions.

It is rare for Pyongyang’s leader to directly mention that his country has the capability to arm ballistic missiles with nuclear warheads, although he implied it on Friday by ordering his troops to put its nuclear arsenal on standby for attack.

The U.S. State Department had immediately called bluff and said that the North has not been confirmed to be able to miniaturize a nuclear weapon.

U.S. Air Force Chief of Staff Gen. Mark Welsh also said during a Pentagon briefing Monday, local time, that North Korea is “not yet at the stage” of mounting a nuclear warhead on a long-range missile yet. Pentagon press secretary Peter Cook also said that the U.S. assessment of the North’s capability remains unchanged.

The North has consistently made efforts to arm nuclear weapons on missiles that can reach contiguous U.S., but the exact missile or nuclear capacity of the hermit kingdom remains a mystery. It also claimed to have conducted a hydrogen bomb test on Jan. 6, but authorities here and in the U.S. have questioned the authenticity of the claim.

While many experts have also raised doubts on the North’s capacity to strike America, David Albright of the U.S. Institute for Science and International Security told media that his group believes North Koreans have already miniaturized a nuclear warhead.

Government officials here have said that North Korea is likely to have “some technology” to miniaturize the warheads, although they are unsure whether it is enough to mount them on ballistic missiles.

“South Korea and the U.S. have yet to acquire intelligence on whether the North can arm nuclear warheads on a ballistic missile,” said a South Korean military official.

His view was echoed by the Unification Ministry spokesman Jeong Joon-hee.

“I think it’s appropriate to say that (Kim’s comment) is one of North Korea’s countermeasures to multiple sanctions by the U.N. and surrounding countries,” he said.

Local observers have predicted that Pyongyang may attempt further provocation after its January nuclear testing and Feb. 7 long-range rocket testing, particularly with South Korea and the U.S. conducting their annual joint military drill from March to April and the convention of the North’s ruling Workers’ Party coming up in May.

In light of rising tension in the Korean peninsula, the allies have commenced possible deployment of the U.S. Terminal High Altitude Area Defense system here. They are also upgrading the Korean Air and Space Operations Center, their command center for combined air operations here.

By Yoon Min-sik (minsikyoon@heraldcorp.com)