The United States will take steps "in time" to have three-way engagements on nuclear deterrence with South Korea and Japan, a senior US diplomat said Wednesday, reiterating America's "firm" security commitment to the Asian allies.

Deputy Secretary of State Kurt Campbell made the remarks, noting ongoing efforts to ensure the credibility of the US' "extended deterrence" commitment through bilateral platforms with the allies in the face of shared challenges, including North Korea's evolving threats.

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

"I believe that we will be taking steps in time to have also trilateral engagements on these topics as well," he said during a forum hosted by the Hudson Institute, a Washington-based think tank.

Campbell mentioned the plan as he touched on Washington's separate nuclear deterrence dialogue with Seoul and Tokyo at a time of deepening trilateral cooperation buoyed by improved relations between the two Asian neighbors long frayed due to historical feuds.

In particular, he pointed to the Washington Declaration that South Korean President Yoon Suk Yeol and US President Joe Biden adopted during a summit last April. The declaration included the launch of the Nuclear Consultative Group, a bilateral platform to discuss nuclear and strategic planning issues.

"I think we've taken substantial steps (for Korea)," he said. "These are designed to make clear that our extended deterrence is solid, and we are determined to take the necessary steps to buttress this message of partnership and the nuclear umbrella extended deterrence applies clearly now as in the past."

Emphasizing the role of America's nuclear umbrella, Campbell warned, "If any one country chose to break out, I think you would have possibly a chain reaction that would be deeply concerning."

Campbell was apparently alluding to a scenario under which a country goes nuclear, leading others to follow suit.

"I think it is a critical component of America's foreign policy and national security to take the necessary steps to reassure leaders that our commitment remains firm," he said.

Campbell cast rapprochement between Seoul and Tokyo as a crucial element of America's drive to bring regional allies and partners in the Indo-Pacific together for cooperation on strategically vital fronts, including technology.

"If we are successful in continuing the path and pace of rapprochement between Japan and South Korea ... if that can continue technologically, politically, strategically and people-to-people, that will have probably the most far-reaching consequential improvement in our partner engagement in the region," he said.

He heaped praise on Yoon and Japanese Prime Minister Fumio Kishida for their fence-mending efforts, noting that their endeavors deserve joint recognition from the Norwegian Nobel Committee, a group responsible for selecting the annual winners of the Nobel Peace Prize.

"If you ask me honestly who deserves the award for really doing something that could make a huge difference on the global stage, I would say that should be a joint award between Kishida and Yoon," he said.

The relations between Seoul and Tokyo took a turn for the better after the Yoon administration announced a decision last March to address the issue of compensating Korean victims of Japan's colonial-era forced labor.

A thaw in the bilateral relations created fresh momentum for the US' longstanding push for trilateral security cooperation, which culminated in the landmark trilateral summit between Yoon, Biden and Kishida at Camp David in August.

With improved relations between Seoul and Tokyo, Biden took a careful approach, Campbell noted.

"I will tell you honestly (that) the president was deeply involved in this, but his goal is to remain in the background," the official said. "He encouraged it, he did phone calls, he supported it, but he recognizes that the American role has to be careful, it has to be nuanced, it has to be subtle, it has to be behind the scenes."

As for various factors creating "anxiety" in the Indo-Pacific, Campbell mentioned China's nuclear buildup, North Korea's military moves and Russia's open threat of nuclear use.

"It used to be that we thought some of the activities that North Korea was taking were somehow to be bartered in some kind of dialogue with the US or with other countries," he said.

"But it's clear that they are determined to create greater capability in a number of areas and to refine capacity, whether it's long-range ballistic missiles or the like ... It's not only their missile launches but their determination to provide capability to Russia." (Yonhap)