President Joe Biden and South Korea's President Yoon Suk Yeol listen to their countries' national anthems together during an official White House State Arrival Ceremony on the South Lawn of the White House in Washington, DC, on April 26.
CNN  — 

President Joe Biden and South Korean President Yoon Suk Yeol announced a key new agreement at the White House on Wednesday that aims to deter North Korean aggression, including a new US commitment to deploy a nuclear-armed submarine in South Korea for the first time since the early 1980s.

In a joint news conference at the White House Biden hailed what he called the “ironclad” alliance between the two countries.

“The alliance formed in war and has flourished in peace,” Biden said from the Rose Garden at the White House. “Our mutual defense treaty is iron clad and that includes our commitment to extend a deterrence – and that includes the nuclear threat, the nuclear deterrent.”

“They’re particularly important in the face of DPRK’s increased threats and the blatant violation of US sanctions,” Biden added.

The product of monthslong discussions between officials from both countries, the new agreement will say that the US “(intends) to take steps to make our deterrence more visible through the regular deployment of strategic assets, including a US nuclear ballistic submarine visit to South Korea, which has not happened since the early 1980s,” the official said. Officials made clear that such assets will not be stationed permanently, and there is “no plan” to deploy any tactical nuclear weapons to the Korean peninsula.

“The bottom line here is there’s even closer cooperation, closer consultation and, and we’re not going to be stationing nuclear weapons on the peninsula, but we will have visits to ports, visits of nuclear submarines and things like that,” Biden said as he heralded the agreement, which he called a “prudent step” to reinforce extended deterrence.

The decision to strengthen extended deterrence – a US policy that uses the full range of military capabilities to defend its allies and position additional American nuclear resources in the region amounts to an acknowledgment that attempts to deter North Korea from advancing its own nuclear program have stalled. Attempts at diplomacy with dictator Kim Jong Un have gone mostly unanswered as the North escalates its missile tests and potentially prepares for another nuclear test.

Warning to Kim

Biden offered a stark warning to Kim in the press conference.

“A nuclear attack by North Korea against the United States or its allies and partners is unacceptable, and will result in the end of whatever regime were to take such an action,” Biden said.

It was direct notice to the North Korean dictator that the United States would defend its treaty ally to his south, and precisely the type of message Yoon arrived in Washington hoping to hear.

“Sustainable peace on the Korean Peninsula does not happen automatically,” Yoon said, “Our two leaders have decided to significantly strengthen extended deterrence of our two countries against North Korea’s nuclear and missile threats so that we can achieve peace through the superiority of overwhelming forces and not a false peace based on the goodwill of the other side.”

Biden welcomed Yoon to the White House for the full pomp and circumstance and hospitality of an official state visit – a high-stakes meeting amid ongoing provocations from North Korea, China’s growing influence in the Indo-Pacific region and a recent leak of Pentagon documents.

As he welcomed Yoon, Biden called the alliance “the linchpin of regional security and prosperity” in the Indo-Pacific.

And more broadly, the visit signals the importance with which the US views its relationships with allies in the Indo-Pacific, this trip coming one week before Biden hosts Philippines President Ferdinand Marcos and weeks before Biden is expected to travel to the region himself.

In the news conference the President also noted the trilateral relationship between US, South Korea and Japan, praising President Yoon’s efforts.

“I want to thank you again Mr. President for your political courage and personal commitment to diplomacy with Japan,” Biden said.

The ‘Washington Declaration’

Biden and Yoon unveiled the “Washington Declaration,” a set of new steps to boost US-South Korean cooperation on military training, information sharing and strategic asset movements in the face of a recent spate of missile launches from North Korea.

It is intended to send a clear message: “What the United States and the ROK plan to do at every level is strengthen our practices, our deployments, our capabilities, to ensure the deterrent message is absolutely unquestioned and to also make clear that if we are tested in any way that we will be prepared to respond collectively and in an overwhelming way,” a senior administration official said.

The declaration includes the deployment of the nuclear ballistic submarine. Additionally, the US and Korea will also “strengthen our training, our exercises and simulation activities to improve the US-ROK alliance’s approach to deterring and defending” against North Korean threats, per the official.

It also creates the “US-ROK Nuclear Consultative Group,” which the official said will convene regularly to consult on nuclear and strategic planning issues, with the hope that it will give allies “additional insight in how we think about planning for major contingencies.” That group is modeled after US engagement with European allies during the height of the Cold War, the official said.

After a year in which North Korea fired a record number of nuclear missile tests, South Korea’s President Yoon earlier this year spoke about possibly deploying US tactical missiles on the Korean peninsula or even developing the country’s own set of nuclear weapons. i

While he dialed back his remarks, those are both scenarios the Biden administration wanted deeply to avoid, and White House officials spent recent months looking for ways to reassure South Korea by bolstering the alliance, including considering a plan to incorporate nuclear exercises into the war planning the two nations already do together, according to two senior Biden administration officials.

“We need to have tabletop exercises that go through a variety of scenarios, including possibly nuclear weapons,” a senior official told CNN earlier this month.

“The South Koreans don’t have experience in using nuclear weapons. This is why we need to do tabletop exercises with them. The Koreans need to be educated in what it means to use nuclear weapons, the targeting, and the effects,” said David Maxwell of the Foundation for Defense of Democracies, adding that there will be no change to the US having control on the targeting. “The hope is that this will satisfy them and improve readiness.”

The hope, the officials said, was that this offer – along with sustained engagement to develop other ideas to implement – will provide the alternative that the South Koreans need.

Also on the agenda

Beyond the declaration, Biden and Yoon are celebrating 70 years of the US-South Korea alliance, highlighting close economic ties between the nations, pointing to cooperation on issues like climate change and the Covid-19 pandemic, and looking toward ways to continue supporting Ukraine amid Russia’s ongoing invasion, plus a new dialogue on cyber cooperation. They are also expected to announce a new student exchange program focused on STEM “that will significantly increase the number of students going in both directions,” a second senior official said.

And Biden praised Yoon for his “courageous, principled diplomacy with Japan,” saying it has “strengthened our trilateral relationship” and “makes an enormous difference.” A stronger alliance between those two countries is strategically important to the US as it looks for ways to counter China’s rising influence.

Leaks loom

Recent online leaks of Pentagon documents involving South Korea also loom over the visit. One of the leaked documents describes, in remarkable detail, a conversation between two senior South Korean national security officials about concerns by the country’s National Security Council over a US request for ammunition.