North Korean leader Kim Jong Un attends a tape-cutting ceremony to mark the completion of a terraced residential district on a bank of the Pothong River in Pyongyang, North Korea, April 13, 2022. KCNA via REUTERS
North Korean leader Kim Jong Un attends a tape-cutting ceremony to mark the completion of a terraced residential district on a bank of the Pothong River in Pyongyang, North Korea, April 13, 2022. KCNA via REUTERS Reuters / KCNA

COVID-19 restrictions may be playing a role in North Korea's lack of response to offers of diplomatic talks, a senior U.S. administration official said on Sunday, a day after President Joe Biden said he had offered vaccines to Pyongyang.

Biden is in South Korea before heading to Japan later on Sunday as part of his first trip through Asia as president.

Meeting with recently elected South Korean President Yoon Suk-yeol on Saturday, Biden vowed to step up efforts to deter North Korean threats but also said he was open to talks - including sitting down with leader Kim Jong Un if necessary - and that he had offered COVID vaccines to Pyongyang with no response.

North Korea has said the U.S. overtures are insincere because Washington maintains "hostile policies" such as military drills and sanctions.

When asked whether Biden was willing to take concrete steps to break the stalemate, the official said that the administration was looking for serious engagement, not grand gestures.

"This is a decision that only the DPRK can make," the official said, using the initials of North Korea's official name.

Biden's focus during the trip has been on rallying "like-minded" democracies to cooperate more, part of broader efforts to counter China's rising influence and exert pressure on Russia over its war in Ukraine.

On the second leg of his first Asia trip as president, Biden will meet with leaders of Japan, India and Australia, a grouping known as the Quad, another cornerstone of his strategy to push back against China's expanding influence.

Yoon has shown interest in working more closely with the Quad, but the U.S. official said there was no current consideration of adding Seoul to the group.

"It's natural... to think about ways in which you can work with other like-minded democracies, but I think it's also important to recognise that the goal right now is to develop and build out what has already been laid out," the official said.

Tokyo will also see the launch on Monday of Biden's long-awaited Indo-Pacific Economic Framework for Prosperity (IPEF), a programme intended to bind regional countries more closely via common standards in areas including supply-chain resilience, clean energy, infrastructure and digital trade.

The U.S. official declined to identify which countries might sign on to the IPEF, but said they were satisfied with "very strong interest" throughout the region in participating.

Before departing to Japan, Biden was scheduled to meet with the chairman of Hyundai Motor Group, which announced new investment in the United States, and tour a U.S. military base with Yoon.