By Joshua Berlinger and Sophie Jeong, CNN

(CNN) -- North Korean leader Kim Jong Un hosted a dinner for a high-ranking South Korean delegation in Pyongyang on Monday, according to a South Korean government official.

It's believed to be the first time the young leader has spoken face-to-face with officials from the South since he took power in 2011. Among those Kim met were South Korea's national security chief, Chung Eui-yong, and the country's spy chief, Suh Hoon.

Their trip north is part of South Korean President Moon Jae-in's attempt to broker a diplomatic solution to North Korea's nuclear weapons program in the wake of the thaw brought about by North Korea's attendance at the PyeongChang Winter Olympics last month.

It's a dramatic departure from 2017, when a string of North Korean weapons tests and hostile rhetoric from US President Donald Trump and Kim heightened tensions on the Korean Peninsula.

"Kim Jong Un as a leader has kept himself highly circumscribed. This is not someone who has met with many non-North Koreans in almost six years," said John Delury, a professor at Yonsei University's Graduate School of International Relations in Seoul.

"It's a major signal of his personal commitment to this process and it gives the South Koreans, for the first time, someone can get a read on Kim Jong Un himself."

The United States has said it would be willing to meet with North Korea, but has always insisted that Pyongyang eventually abandon its nuclear weapons program as part of any talks.

In a speech at the exclusive Gridiron Club Saturday night -- an annual event in which the President gets together with other political leaders to deliver joke-laden, self-deprecating speeches -- Trump touched upon the North Korea issue.

"They called up a couple of days ago and said, 'We would like to talk,'" Trump said. "And I said, 'So would we, but you have to de-nuke. You have to de-nuke.' So let's see what happens. Let's see what happens."

North Korea's Foreign Ministry, for its part, accused the US this weekend of refusing to recognize realities on the ground and putting forward unrealistic roadblocks to dialogue.

Shy of foreigners

To date, Kim has met few foreigners since taking control of the hermit state. He's hosted former basketball star Dennis Rodman on multiple occasions and was photographed clasping hands with Liu Yunshan, a former top leader of China's Communist Party, at a military parade in 2015.

Kim did not appear to meet with a senior Chinese envoy who was sent to North Korea for rare talks in November 2017. Former US Director of National Intelligence James Clapper did not meet Kim when he traveled to North Korea for a rare visit nearly four years ago.

Momentum

The Olympic detente has been an opportunity for the Moon administration to try to prevent an escalation of last year's tensions.

"There's a clear determination on Moon's part not to lose momentum after the Olympics," said Euan Graham, the director of the international security program at the Lowy Institute, an Australian think tank.

To that end, the South Korean delegation in Pyongang will "have an in-depth discussion on measures to continue various talks between North Korea and the international community, including the United States," according to Chung.

"Above all, I will communicate clearly the will and intention of the president, who wants the de-nuclearization of the Korean Peninsula, and create a lasting peace by utilizing the flow of the inter-Korean dialogue," Chung said.

Moon, who was elected last year after his conservative predecessor was ousted in a corruption scandal, has been proponent of dialogue and engagement with North Korea since his days as a presidential aide in the 2000s.

Now he has the difficult job of playing interlocutor between a North Korean regime steadfastly clinging to its nuclear weapons program -- which it sees as the only way to ensure the survival of its regime -- and an administration in Washington that believes Pyongyang's development of a long-range ballistic missile potentially capable of hitting the US homeland with a nuclear warhead constitutes an unacceptable risk.

"What Moon is trying to do is interpose himself between North Korea and the United States so that there is a kind of defusing role that the South Koreans play, naively or not, in trying to at least sort of forestall any ramping up of tensions," Graham said.

Another trip north?

Though Chung is officially leading the delegation, the attendance of Suh could signal that the two sides are laying the groundwork for Moon to eventually meet with Kim in person.

Moon was invited north last month by Kim's sister, Kim Yo Jong, who also serves as the head of the country's propaganda department. She was in South Korea last month to attend the Winter Games opening ceremony.

Suh was tapped by Moon to serve as the director of South Korea's National Intelligence Service. His appointment fueled speculation about a new inter-Korean summit, as Suh helped organize the two inter-Korean summits in the 2000s that saw two consecutive South Korean presidents travel north to meet with Kim Jong Il.

Sending Suh to Pyongyang "suggests they're already taking about summit preparations," said Graham.

The delegation will spend Monday night in Pyongyang, return to Seoul on Tuesday and then travel to the United States to brief their American counterparts.

What happens next

Many observers worry about what happens to the diplomatic thaw once the Olympic activities finish.

South Korea and the United States are scheduled to hold annual military drills after the Paralympics, South Korean Defense Ministry spokeswoman Choi Hyun-soo confirmed Monday.

Those drills, which North Korea views as hostile, were delayed in order to ensure the Games went smoothly.

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