North Korean leader Kim Jong Un’s younger sister, Kim Yo Jong, attended the opening ceremony of the Pyeongchang Winter Olympics in South Korea on Friday, a historic moment that brings hope for easing security tensions sparked by Pyongyang’s nuclear weapons ambitions.

During the ceremony, Kim Yo Jong, who is a member of North Korea’s high-ranking delegation to the Olympics and considered one of the closest aides to her brother, shook hands with South Korean President Moon Jae-in on their first encounter, TV footage showed.

When North and South Korean athletes jointly marched into the stadium under a unified Korean flag, Kim, wearing a black coat, waved with Moon before shaking hands again as they stood together with the other delegates from Pyongyang.

Kim arrived by plane earlier in the day. She has become the first immediate family member of North Korea’s founder Kim Il Sung to ever set foot in the South.

At a reception dinner prior to the ceremony, North Korea’s ceremonial leader Kim Yong Nam, who leads the delegation, also shook hands with Moon while exchanging a few words with smiles.

The delegation and Moon are scheduled to hold a meeting on Saturday, the South Korean government said.

It is rare for a South Korean president to hold formal talks with high-ranking officials from the North. The two countries technically remain at war because the 1950-53 Korean War ended in a cease-fire.

CNN reported Friday that during a luncheon between the delegates and Moon, Kim Yo Jong may invite the president to visit Pyongyang sometime this year, citing several diplomatic sources with deep knowledge of the North’s intentions.

The report said one potential date for a visit is Aug. 15, the anniversary of Japan’s surrender in World War II and the Korean Peninsula’s liberation from decades of Japanese colonial rule.

The South Korean media, meanwhile, have floated the possibility that the delegation may deliver a personal letter or message to Moon from Kim Jong Un himself.

Observers say that by sending Kim’s younger sister, the North is trying to underscore the recent rapprochement with the South while testing the unity of South Korea, the United States and Japan, which are enforcing sanctions imposed on Pyongyang for its nuclear and missile programs.

A jetliner carrying the high-level delegation flew into Incheon International Airport shortly before 2 p.m. South Korean TV later showed footage of the delegation catching a high-speed train to Pyeongchang, the main Olympic venue in the east.

North Korean airline Air Koryo is subject to sanctions imposed by the United States and South Korea. But an official of the South’s Unification Ministry signaled that the plane used by the delegation would not be subject to the sanctions.

The plane was expected to return to the North and return to the airport on Sunday to pick up the delegation, according to the ministry.

Also in the delegation are Choe Hwi, chairman of the National Sports Guidance Committee, and Ri Son Gwon, head of the Committee for Peaceful Reunification of Fatherland, a state agency in charge of handling inter-Korean affairs.

Choe is subject to a travel ban and assets freeze under a U.N. Security Council resolution adopted June 2, but a U.N. committee on North Korea sanctions on Thursday granted him a temporary exemption to attend the Winter Olympics.

Kim Yong Nam is president of the Presidium of the Supreme People’s Assembly.

Roughly two dozen North Korean athletes are competing in such disciplines as women’s ice hockey, figure skating and short-track speed skating during the games, which run until Feb. 25.