Seoul: North Korea's reclusive leader, Kim Jong Un, extended an extremely rare invitation to a foreign head of state, using the diplomatic opening created by the Olympics in South Korea to ask its leader, President Moon Jae-in, to visit the North for a summit meeting.

Kim's unusual invitation, which was received by Moon with both caution and optimism, was the latest sign of warming relations between the two rival governments after an exceptionally tense period over the North's nuclear weapons program.

But the overture by the North also risked driving a wedge between South Korea and the United States, its main military ally, which has been campaigning for "maximum sanctions and pressure" against North Korea.

Vice President Mike Pence, who was visiting South Korea for the Olympics, has used increasingly hostile language against the North in recent days, calling it the most tyrannical regime on the planet and steadfastly avoiding interactions with North Korean delegates at the games.

Kim sent the invitation to the South through a particularly close and trusted envoy: his only sister, Kim Yo Jong. She is one of the reclusive leader's closest advisers and met with Moon at the presidential Blue House in the capital, Seoul, on Saturday in the highest-level contact between the two Koreas in years.

The Trump administration is wary of engagement with the North, which has been subjected to increasingly tough international sanctions, unless it shows clear signs of giving up its nuclear weapons program.

Pence — who sat just feet away from Kim Yo Jong at the Olympic opening ceremony, with neither apparently speaking to the other — has also been critical of the North's participation in the games, seeing it as an attempt to create a division between the United States and the South.

South Korea's president, Moon, welcomed the possibility of a meeting with the North Korean leader, saying the two Koreas should "work together to create the environment to make it happen," a spokesman said.

But Moon has also said that he would be willing to meet Kim only if he received assurances that the North would help resolve the crisis over its nuclear weapons program.

"The South and North shared an understanding that they should continue the positive mood for peace and reconciliation created by the Pyeongchang Olympics and should promote inter-Korean dialogue, exchanges and cooperation," Moon's office said in a statement.

If Moon accepts Kim's offer to come to the North, it will be the third summit meeting between the two Koreas. But it would be Kim's first meeting with a foreign head of state.

Kim Jong Il, Kim's father, had met with two South Korean presidents in Pyongyang, the North Korean capital, before his death in 2011: with President Kim Dae-jung in 2000, and with President Roh Moo-hyun in 2007.

Both of those South Korean presidents faced growing domestic criticism after their trips to Pyongyang had resulted in large shipments of aid and investment but failed to end the North's nuclear weapons program.

Moon also urged North Korea to talk to the United States, his office said. In the past, he has said that there was a limit to how much the Koreas' ties could improve without a resolution of the nuclear weapons issue. In a news conference last month, he said he was not interested in "talks for talks' sake."

North Korea's leader, Kim, once dismissed as an inexperienced figurehead, has quickly built a reputation as a ruthless dictator at home and a wily strategist in handling North Korea's external enemies. Since he took power six years ago, he has not only executed scores of senior party officials and military generals but also rattled the region by accelerating nuclear and missile tests.

He has gotten closer to completing nuclear missiles capable of hitting the United States than his father and grandfather, who had ruled before him, had ever hoped for, and did do with a heavy cost: increasingly biting sanctions. Now, Kim, 34, has switched tactics to a charm offensive aimed at persuading South Korea to break ranks with Washington, analysts said.

Moon's government is clearly more optimistic than the Trump administration about the potential for the Koreas' cooperation at the Olympics to create the groundwork for more substantial discussions. At a reception Friday, Moon pointed to the joint Korean women's ice hockey team — an Olympic first — as a starting point.

"The female ice hockey players from the two Koreas are now holding a small snowball in their hands," he said. "Now, if we put our hearts and minds together, it will continue to grow larger and larger and turn into a snowman of peace."

Moon joined Kim Yo Jong and other North Korean supporters Saturday in cheering for the team against Switzerland. The supporters waved blue and white flags that showed an undivided Korean Peninsula.

North and South Korea marched under one flag at the Olympics' opening ceremony. Some South Koreans hope it is a symbol of a peaceful unification. Others fear it is an omen of larger political ambitions of the North.

Pence, by contrast, avoided speaking with North Korean officials on Friday, and he and his wife did not stand, as most spectators did, when the athletes from both Koreas marched together under a flag representing a unified Korea. Earlier Friday, Pence met with defectors from the North and invited them to tell their stories of repression under Pyongyang.

Moon would like to bring both North Korea and the United States to the negotiating table. China has suggested that talks could start if the United States suspended its regular joint military exercises with South Korea, and if North Korea reciprocated by shelving nuclear and missile tests.

But both sides have held their ground. North Korea has said that its nuclear weapons are not for bargaining away. In a speech that Kim gave on New Year's Day, in which he first raised the possibility of the North participating in the Olympics, he vowed to "mass-produce" nuclear weapons and missiles.

Pence reiterated Friday that the North must "put denuclearization on the table and take concrete steps with the world community to dismantle, permanently and irreversibly, their nuclear and ballistic missile programs."

"Then, and only then, will the world community consider negotiating and making changes in the sanctions regime that's placed on them today," Pence said after a meeting with Moon.

"Kim Jong Un has no intention of giving up his nuclear weapons," said Cheon Seong-whun, a former presidential secretary for security strategy and now a visiting research fellow at the Asan Institute for Policy Studies in Seoul. "With his summit proposal, he seeks to incite friction between Seoul and Washington by widening their policy gap."

New York Times