The United States will not accept North Korea as a nuclear-armed country, a senior US diplomat said Wednesday, after Pyongyang made a rare disclosure of a uranium enrichment facility last week.

During a hearing of the House Foreign Affairs Committee, Deputy Secretary of State Kurt Campbell reiterated the US position, reaffirming America's "durable" and "evolving" deterrence commitment to South Korea, and stressing that Washington "will not accept any kind of threat" to the Asian ally.

On Friday last week, the North's state media reported that leader Kim Jong-un had visited a uranium enrichment facility, in the first disclosure of such a site since the regime invited Siegfried Hecker, a US nuclear scientist, to its uranium enrichment facility at Yongbyon, north of Pyongyang, in 2010.

"I will just say diplomatically, we're prepared to sit down and engage with North Koreans," Campbell said. "We do have some conditions. We will not accept North Korea as a nuclear state."

Expressing concerns that deepening cooperation between the North and Russia would embolden them to take more provocative steps, Campbell highlighted that the "best answer" is deeper trilateral security cooperation between South Korea, the US and Japan.

"We've undertaken (trilateral cooperation efforts). Also, we've undertaken steps to make clear that our extended deterrence is strong, it's durable and evolving to make clear that we will not accept any kind of threat to the ROK and the people living on the peninsula," he said, referring to South Korea by its official name, the Republic of Korea.

Extended deterrence refers to America's commitment to using the full range of its military capabilities, including nuclear, to defend its ally.

"So I think the steps of deterrence, of forward deployment, of engagement, working with allies and partners ... that message of determination is unmistakable in Pyongyang," he added.

Regarding a question over whether Washington will enter negotiations only after the North's abandonment of its nuclear program, Campbell underscored Pyongyang's unwillingness to talk.

"I will tell you all of our engagements are attempts. We wanted to help, to assist during COVID. We wanted to open the door," he said. "For the last six years, we've had virtually no communication with North Korea. They have chosen not to engage with us directly."

The hearing came as Pyongyang has ratcheted up tensions with a set of weapons tests, a disclosure of a nuclear facility and continued tough rhetoric, with the US presidential election less than seven weeks away.

The North's saber-rattling has added to concerns that the recalcitrant regime could engage in major provocations near the US general election to bolster its leverage.

Asked if the North Korean leader has a malign influence on US interests in the Indo-Pacific, Campbell agreed.

"I would say clearly, Kim Jong-un is undertaking deeply malign steps against American strategic interests, against our closest partners in Japan and South Korea," he said. "I do not believe there are any redeeming features about their role on the global stage."

Campbell reiterated concerns about North Korea's arms support for Russia as well as China's support for Russia's defense industrial base.

"Almost every weapon system that the Russians have utilized on the battlefield in their illegal war have component pieces or chips or other things that have come from foreign sources, many from China. We see signs of North Korean weapons systems -- artillery rounds, larger-range missiles -- that are collected on the battlefields of Ukraine," he said.

"North Korea is about the most heavily sanctioned country in the world. We've still added on a few sanctions as a result."

He noted the need for more European countries to speak out against China's steps in support of Russia. (Yonhap)