In his first trip to Asia since taking office, President Joe Biden laid out conditions for meeting with North Korea’s Kim Jong Un.

“With regard to whether I would meet with the leader of North Korea, that would depend on whether he was sincere and whether he was serious,” Biden told reporters on Saturday as he appeared alongside South Korean President Yoon Suk-yeol at a press event.

Biden campaigned on taking a tougher stance on the North Korean leader than his predecessor. Former President Donald Trump frequently praised Kim, once saying he had a “great and beautiful” vision for his country. Trump and Kim held three high-profile meetings during his presidency.

Biden said last year he’d only meet with Kim so long as he committed to a discussion about dismantling North Korea’s nuclear arsenal.

“What I would not do is what has been done in the recent past,” Biden said at the time. “I would not give him all he’s looking for, international recognition as legitimate, and give him what allowed him to move in a direction of appearing to be more serious about what he wasn’t at all serious about.”

Yoon, South Korea’s newly elected president, reaffirmed Saturday that their shared goal is the complete denuclearization of North Korea.

Biden said Saturday that the U.S. has offered vaccines to North Korea without any preconditions but has received no reply. Coronavirus appears to be surging in North Korea, with 2.4 million people “sickened with fever” as of Thursday.

“The answer’s yes, we’ve offered vaccines, not only to North Korea, but to China as well,” Biden said. “And we’re prepared to do that immediately. We’ve gotten no response.”

A White House spokesperson said the U.S. has offered to provide the shots through existing programs like COVAX — a global initiative to supply COVID-19 vaccines — as recently as last week.

During the joint news conference in Seoul, Biden and Yoon discussed ramping up U.S. support for South Korea in the face of North Korea’s aggression.

“Today, President Yoon and I committed to strengthening our close engagement and work together to take on challenges of regional security, including addressing the threat posed by the Democratic People’s Republic of Korea by further strengthening our deterrence posture and working towards complete denuclearization of the Korean Peninsula,” Biden said.

Both leaders agreed to consider expanding combined military exercises and training on the Korean Peninsula.

Biden began his six-day trip in South Korea on Friday and will end the trip in Tokyo, Japan, where he’ll meet with Japanese Emperor Naruhito and Prime Minister Kishida Fumio.

The White House said the trip comes at a pivotal moment in Biden’s foreign policy agenda.

“The message we’re trying to send on this trip is a message of an affirmative vision of what the world can look like if the democracies and open societies of the world stand together to shape the rules of the road, to define the security architecture of the region, to reinforce strong, powerful, historic alliances,” National Security Adviser Jake Sullivan told reporters this week.