Representational photo: A U.S. Air Force B-52H Stratofortress preflight crew with the 20th Expeditionary Bomb Squadron works in the cockpit before launching an early morning sortie from Royal Australian Air Force (RAAF) Base Darwin, Australia, April 3, 2018. (U.S. Air Force photo by Staff Sgt. Alexander W. Riedel via U.S. Defense Visual Information Distribution Service)

By Trevor Hunnicutt, Steve Holland and David Brunnstrom

WASHINGTON (Reuters) -The U.S. on Wednesday pledged to give South Korea more insight into its nuclear planning over any conflict with North Korea amid anxiety over Pyongyang's growing arsenal of missiles and bombs.

The announcement, which included a renewed pledge by Seoul not to pursue a nuclear weapons program of its own, emerged from White House talks between U.S. President Joe Biden and South Korean leader Yoon Suk Yeol that covered issues including North Korea, chips and trade and the Ukraine war.

At a joint news conference, Yoon announced that he and Biden had agreed on steps to strengthen South Korea's defenses in response to the threat posed by North Korea.

"Our two countries have agreed to immediate bilateral presidential consultations in the event of North Korea'snuclear attack and promised to respond swiftly, overwhelmingly and decisively using the full force of the alliance, including the United States nuclear weapons," Yoon said.

Biden again reiterated the U.S. offer to North Korea to hold diplomatic negotiations over its nuclear and missile programs, an offer that has been ignored by North Korean leader Kim Jong Un.

North Korea’s mission to the United Nations did not immediately respond to a request for comment. 

DETERRING NORTH KOREA

North Korea's rapidly advancing weapons programs - including ballistic missiles that can reach U.S. cities - have raised questions about whether the U.S. 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.

Under a new "Washington Declaration," the U.S. will give South Korea detailed insights into, and a voice in, U.S. contingency planning to deter and respond to any nuclear incident in the region through a U.S.-ROKNuclear Consultative Group, U.S. officials said.

As part of the deal, Washington will deploy a ballistic-missile submarine to South Korea in a show of force. It will be the first such submarine visit since the 1980s, U.S. officials said.

But Biden made clear no U.S. nuclear weapons would be stationed on South Korean territory.

“I have absolute authority as commander in chief and the sole authority to use a nuclear weapon, but … what the declaration means is that we're going to make every effort to consult with our allies when it's appropriate, if any action is so called for," Biden said.

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.

A "WIN" FOR SOUTH KOREA

Duyeon Kim, an analyst with the Center for a New American Security, called the Washington Declaration "a big win for the alliance and especially for South Korea."

"It looks like Yoon got everything he wanted this time and more. For the first time, the allies are discussingnuclear deterrence, which Seoul has not been able to discuss with Washington until now," she said.

Daniel Russel, the top U.S. diplomat for East Asia under former President Barack Obama, said it was important for Yoon to avoid a perception among South Koreans that he gave much but got too little from his Washington visit.

“So what Yoon needs from Washington needs to go beyond a repeat of rhetorical assurances and include a process that enables South Korea to engage and participate more directly in extended deterrence," Russel said.

After the talks and news conference, the two leaders were to attend a glittering state dinner catered by a U.S. chef whose mother emigrated from Korea.

The summit also produced agreements on cyber security, electric vehicles and batteries, quantum technology, foreign assistance and economic investment.

The officials stressed that no U.S. nuclear weapons would be returned to the peninsula, and South Korea would continue not to have control over the U.S. nuclear arsenal.

The U.S. planned to brief China before the steps, the officials said, signaling desire to ease a tense relationship.

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.

(Reporting by Trevor Hunnicutt, Steve Holland and David Brunnstrom; Editing by Scott Malone, Michael Perry, Nick Macfie, Josie Kao and Don Durfee)