President Yoon Suk Yeol returned home Sunday wrapping up a seven-day state visit to the United States.

Yoon and US President Joe Biden discussed ways to strengthen extended deterrence and released the Washington Declaration separately from a joint summit statement.

The gist of the declaration is the establishment of a new bilateral nuclear consultative group and the regular deployment of US strategic assets in South Korea.

The Washington Declaration is significant in that US capabilities to back its extended deterrence includes nuclear assets. The declaration has expanded the US-Korea alliance from conventional to nuclear capabilities.

The upcoming visit of a US nuclear ballistic missile submarine to South Korea can be seen as a step in response to public opinion among South Koreans that their country needs to be nuclear armed. Biden’s remarks that he has absolute authority as commander-in-chief to use a nuclear weapon but that the US will consult with its allies when it's appropriate can be understood in the same context. His words are a message that he cannot agree to South Korea going nuclear. In the Washington Declaration, Seoul reaffirmed its non-proliferation obligations under the Treaty on the Non-Proliferation of Nuclear Weapons.

Instead, the US nuclear deterrence must be overwhelming enough to prevent North Korea from using its nuclear weapons. Despite sanctions and pressure from the international community, the North has been developing atomic bombs and missiles incessantly. It threatens to fire them at the US. The Washington Declaration seems to fall somewhat short of discouraging the North’s nuclear ambitions.

But Pyongyang must listen carefully to President Biden’s warning. He said in a joint press conference after his summit with Yoon that “a nuclear attack by North Korea against the United States or its allies or partners is unacceptable and will result in the end of whatever regime, were it to take such an action.”

US officials have sometimes mentioned the change of regime. It is the first time for Biden to mention publicly the end of the North Korean regime in connection to its nuclear threat. The end of the regime is a much stronger warning against the North which recently escalated its missile provocations. The only way for the Kim Jong-un regime to survive is to give up nuclear weapons and return to dialogue.

The nuclear consultative group will hold regular meetings and consultations to share information on nuclear assets and intelligence and work to enable joint execution and planning for South Korean conventional support to US nuclear operations. The US will deploy its strategic assets such as submarines and bombers mounted with nuclear weapons to South Korea more often. This is a big change in the US' stance.

The group is said to be modeled after the NATO Nuclear Planning Group. NATO allies retain political control of all aspects of nuclear decision-making. The planning group’s discussions cover a broad range of nuclear policy matters, including the overall effectiveness of NATO’s nuclear deterrent. It is unclear if South Korea will have as much influence in the consultative group as that of NATO in the planning group.

Edgard Kagan, special assistant to President Biden and senior director for East Asia and Oceania of the National Security Council, said Thursday that he does not think that the Washington Declaration is a de facto “nuclear sharing” agreement. His remarks were an apparent refutation of what a South Korean official said a day earlier. Kim Tae-hyo, deputy national security adviser, argued that the declaration will make the people of South Korea “feel that they are sharing nuclear weapons with the United States.” Kim seems to have stretched the meaning of the declaration.

The declaration may have left something to be desired, but it is desirable to resolve issues through consultation.

Obviously, the declaration showed a strong commitment to deter the North from using a nuclear weapon. From now on, Seoul and Washington must focus on raising the effectiveness of nuclear deterrence through the group.