WASHINGTON-- The United States will continue to build its defense capabilities against North Korea's evolving nuclear threats, a US National Security Council spokesperson said Tuesday, noting the North continues to ignore US overtures for dialogue.

John Kirby, NSC coordinator for strategic communications, also highlighted the importance of joint South Korea-US military exercises.

"We are well aware that Kim Jong-un continues to fire off missiles and he continues to try to improve the capabilities of his ballistic missile program and continues to pursue nuclear ambitions as well," Kirby told a virtual press briefing when asked what the US was doing to curb advancements in North Korea's nuclear weapons program.

Kirby declined to comment on the US' intelligence assessment of North Korea's nuclear arsenal, but said, " What I can tell you has not changed is our desire to sit down with the regime in Pyongyang without precondition to find a diplomatic way forward to the denuclearization, verifiable denuclearization of the peninsula."

North Korean leader Kim on Monday called for increased production of "weapons-grade" fissile materials to build more nuclear weapons, while also calling for flawless preparations for the use of nuclear weapons at "anytime and anywhere," according to reports by the North's Korean Center News Agency.

Kirby said the North has not shown "any willingness" to engage in dialogue with the US

"So we do what we must do, which is to meet our treaty requirements or security requirements there on the peninsula and the region," he said.

"And so we will continue to make sure that we have the appropriate military capabilities and the appropriate readiness to use those capabilities if need be, to protect our national security interests and those of our allies," added Kirby.

North Korea has been intensifying its rhetoric against US-South Korea joint military drills, calling them "war rehearsals" that they claim are aimed at preparing the allied forces for their eventual invasion of the North.

Kirby stressed the importance of joint military drills after many other US officials said the exercises are "longstanding, routine" exercises that are "purely defensive in nature."

"We believe that they (joint military exercises) will help us with those readiness capabilities," said Kirby.

"We still would like to see a diplomatic solution this. There's been no light on that coming from Pyongyang, so we are going to have to continue to make sure we are ready for defend our interests there," he added. (Yonhap)