WASHINGTON -- The recent agreement reached between South Korea and the United States on strengthening US extended deterrence is a significant step in dealing with North Korea's evolving nuclear threat but possibly not the last step to be taken by the allies, US experts said Tuesday.

They also insisted that while the agreement, dubbed the Washington Declaration, may enhance the allies' joint deterrence against North Korea, it may fall short of preventing future provocations by the reclusive North.

"The declaration says the US "commits to make every effort to consult with the ROK on any possible nuclear weapons employment on the Korean Peninsula,"" said Elaine Bunn, former deputy assistant secretary of defense for nuclear and missile defense policy.

ROK stands for the Republic of Korea, South Korea's official name.

"You know that the use of US nuclear weapons is a decision that only the US president is authorized to make. So the commitment at the presidential level to make every effort to consult is very significant," she added in a webinar hosted by the Stimson Center, a Washington-based think tank.

The Washington Declaration, signed by US President Joe Biden and South Korean President Yoon Suk Yeol late last month, calls for the establishment of a Nuclear Consultative Group between the allies, which US officials have said will allow more South Korean input into how the US prepares against a possible nuclear weapons use by North Korea.

Some have even likened the NCG to NATO's Nuclear Planning Group, although US officials have noted that the Washington Declaration is not a "nuclear-sharing" agreement.

"My observations are that consultations are not new, but the Washington Declaration raises the level and further institutionalizes those consultations with the Nuclear Consultative Group," Bunn told the virtual seminar.

"And planning together is not new, but the Washington Declaration is an evolution toward greater integration of planning and assets for deterrence, both those of the US and those of South Korea," she added.

Curtis Scaparrotti, a retired US Army general who served as commander of US Forces Korea and US European Command, said the Washington Declaration and the provisioned NCG are uniquely designed to deal with threats specific to the region.

"As I watch the North Korean development of its nuclear capabilities in numbers, range and diversity of systems, it's clear that the deterrence and defense of the ROK-US alliance has to adapt as well," he said.

"I believe the Washington Declaration, despite the criticisms that we have heard and discussed and I've read about, it outlines an effective way ahead for strengthening the ROK-US alliance, reassuring the ROK populace in deterring evolving North Korean threat," he added.

The experts, however, noted that the allies may be required to take additional steps to further strengthen US extended deterrence as North Korea's nuclear threat continues to evolve.

"I just think that the whole nature of extended nuclear deterrence ... is a constant," said Bunn.

"It is a constantly evolving situation, and I think there will be further evolutions. We have seen evolution so far in how we discuss together, plan together ... We will continue to see that evolution. So we shouldn't think that this is the end," she added.

Scaparrotti argued the Washington Declaration may have little to do directly with deterring North Korean provocation.

"I would remind you that these processes and commitments that I'm talking about are a process and not an end state. Therefore, they won't be the perfect response. The ROK-US alliance will have to adapt as it moves along," he said.

"Our deterrence is aimed at one thing; aggression. So the idea that we are going to stop their provocations, et cetera, through nuclear deterrence, that's not at all the case," he added. "And I think there needs to be a clear understanding of what that nuclear deterrent is for. It's for aggression."

Joel Wit, a senior researcher at the Stimson Center, noted the declaration may have partly been driven by South Korea's desire to arm itself with its own nuclear weapons.

"The political and public pressures in South Korea that I think are a big factor driving forward, and so for me, I feel like we are on a slippery slope that the Washington Declaration may be a good step, it may deal with the problem right now, but we may be having a different conversation a year (from now) that will require more steps," he said. (Yonhap)