US President Joe Biden and South Korean leader Yoon Suk Yeol held White House talks on Wednesday to deepen collaboration on deterring North Korean nuclear escalation amid anxiety about its growing arsenal of missiles and bombs.
"Today we celebrate the ironclad alliance, the shared vision of our future and a deep friendship -- the Republic of Korea and the United States," Biden said in welcoming Yoon to the White House during a pomp-filled arrival ceremony.
Yoon said he wanted to celebrate 70 years of ties between the US and South Korea.
"The ROK-US alliance is an alliance of values, standing together to safeguard the universal value of freedom," Yoon told thousands gathered on the South Lawn of the White House.
After a day of talks and a joint news conference, the two leaders were to attend a glittering state dinner catered by a US chef whose mother emigrated from Korea.
Biden and Yoon were using the first formal state visit by a South Korean leader in more than a decade to send a warning to North Korean leader Kim Jong Un.
North Korea's rapidly advancing weapons programs - including ballistic missiles that can reach US cities - has raised questions about whether the US would really use its nuclear weapons to defend South Korea under what it calls "extended deterrence."
Opinion polls in South Korea show a majority of the public wants Seoul to acquire its own nuclear bombs, a step Washington opposes.
White House national security spokesperson John Kirby told a briefing the summit was expected to produce "major deliverables" on issues like extended deterrence, cyber security, climate mitigation, foreign assistance and economic investment.
Under a new "Washington Declaration," the US will give South Korea detailed insights into, and a voice in, US contingency planning to deter and respond to any nuclear incident in the region through a US-ROK Nuclear Consultative Group, US officials said.
While the allies will make a fresh appeal to North Korea to engage in diplomacy, Washington will deploy imposing military technology, including a ballistic-missile submarine, to South Korea in a show of force, senior US administration officials told reporters in a briefing call. It will be the first such submarine visit since the 1980s, they said.
The officials stressed that no US nuclear weapons would be returned to the peninsula, and South Korea would continue not to have control over the US nuclear arsenal.
South Korea will also reaffirm its commitment to the nuclear non-proliferation treaty and its non-nuclear status, they said.
"This is modeled after what we did with European allies during the height of the Cold War in similar periods of potential external threat," said one senior Biden administration official.
The agreed steps fall short of what some in South Korea have called for and are unlikely to alter the direction of North Korea's own nuclear program. But they could allow Yoon to argue to his domestic audience that Washington is taking South Korea's concerns seriously.
The US is briefing China in advance on the steps, the officials said, a measure nodding to desires to ease the tense relationship in the region.
It is only the second state visit Biden has hosted since he took office two years ago - the first such guest was France's president.
For all the extravagance, Yoon's visit comes at a moment of high anxiety in the region.
A poll released on April 6 by the Asan Institute for Policy Studies in Seoul found 64% of South Koreans supported developing nuclear weapons, with 33% opposed.
Yoon, in an interview with Reuters last week, signaled for the first time a softening in his position on providing weapons to Ukraine, saying his government might not "insist only on humanitarian or financial support" in the event of a large-scale attack on civilians or a "situation the international community cannot condone." The topic is expected to be discussed on Wednesday, along with climate change and cybersecurity.
Washington has looked fondly on Yoon's willingness to help on Ukraine and seek rapprochement with Japan, the other key US ally in northeast Asia, and on the wave of Korean tech investment in the US since he took office, which officials say now approaches $100 million.
