U.S. President Joe Biden is willing to meet with North Korean leader Kim Jong Un "without preconditions" to discuss the denuclearization of the Korean Peninsula, a senior White House official said Thursday.

"They have not responded positively to that offer, but it's still on the table. We are willing to sit down and negotiate without preconditions," White House national security spokesman John Kirby said in an interview with Kyodo News.

White House national security spokesman John Kirby speaks during an interview at the White House in Washington on Aug. 17, 2023. (Kyodo)

Kirby made the remarks a day before Biden is set to host a trilateral summit with the leaders of Japan and South Korea, at which North Korea's rapid development of nuclear and missile capabilities will be a major agenda item.

Unlike his predecessor Donald Trump, who met with Kim in person three times, Biden's administration has sought to make progress toward denuclearization through multiple channels involving officials, but not at the top level.

The offer of a top-level meeting, disclosed by Kirby without specifying when the offer was made, suggests the Biden administration is stepping up efforts to reach out to North Korea.

In a related development, Mira Rapp-Hooper, National Security Council senior director for East Asia, revealed at a think tank event on Wednesday that the administration has been making a particular effort to invite North Korea to come to the table in recent weeks.

She said that such attempts have intensified since a U.S. soldier stationed in South Korea crossed the heavily armed border into North Korea without authorization a month ago.

Referring to Pyongyang's lack of response to the Biden administration, Kirby said, "But absent that, and thus far he has shown no interest in that, we've got to make sure that we are ready in every other respect to defend our national security interests and those of our Korean and Japanese allies."

"That means putting more capability in the region which we have, and we will certainly consider doing that again in the future if we have to," he added.

South Korea's spy agency has detected signs that North Korea is preparing to launch an intercontinental ballistic missile to coincide with the first-ever standalone three-way summit, a South Korean lawmaker said Thursday.

Kirby said that "there could be some sort of provocative action, but we just don't know what that's going to look like and it wouldn't be a good use of our time in worrying too much about that."

At the U.S. presidential retreat of Camp David near Washington, Biden, Japanese Prime Minister Fumio Kishida and South Korean President Yoon Suk Yeol will agree to boost their deterrence capabilities to better respond to North Korea's belligerence as well as China's rising military power, according to senior officials who are involved in preparations for the summit.

Related coverage:

Japan PM vows to bolster ties with U.S., South Korea to tackle North Korea

North Korea preparing ICBM launch to protest trilateral summit: South Korea

U.S., Japan, South Korea summit to include agreement on new hotline