People watch a TV broadcasting file footage of a news report on North Korea firing a ballistic missile off its east coast, in Seoul, South Korea, October 19, 2021. REUTERS/Kim Hong-Ji

People watch a TV broadcasting file footage of a news report on North Korea firing a ballistic missile off its east coast, in Seoul, South Korea, October 19, 2021. REUTERS/Kim Hong-Ji

People watch a TV broadcasting file footage of a news report on North Korea firing a ballistic missile off its east coast, in Seoul, South Korea, October 19, 2021. REUTERS/Kim Hong-Ji

People watch a TV broadcasting file footage of a news report on North Korea firing a ballistic missile off its east coast, in Seoul, South Korea, October 19, 2021. REUTERS/Kim Hong-Ji

People look at North Korea's propaganda village Kaepoong through binoculars from the top of the Aegibong Peak Observatory, south of the demilitarised zone (DMZ), separating the two Koreas in Gimpo, South Korea, October 5, 2021. REUTERS/Kim Hong-Ji

North Korean citizens work on a rice field in North Korea's propaganda village Kaepoong in this picture taken from the top of the Aegibong Peak Observatory, south of the demilitarised zone (DMZ), separating the two Koreas in Gimpo, South Korea, October 5, 2021. REUTERS/Kim Hong-Ji

A genearl view of a rice field in North Korea's propaganda village Kaepoong in this picture taken from the top of the Aegibong Peak Observatory, south of the demilitarised zone (DMZ), separating the two Koreas in Gimpo, South Korea, October 5, 2021. REUTERS/Kim Hong-Ji

A man takes photographs of North Korea's propaganda village Kaepoong from the top of the Aegibong Peak Observatory, south of the demilitarised zone (DMZ), separating the two Koreas in Gimpo, South Korea, October 5, 2021. REUTERS/Kim Hong-Ji

A general view of pairs of binoculars from the top of the Aegibong Peak Observatory, south of the demilitarised zone (DMZ), separating the two Koreas in Gimpo, South Korea, October 5, 2021. REUTERS/Kim Hong-Ji

A general view of the North Korean guard posts, in this picture taken from the top of the Aegibong Peak Observatory, south of the demilitarised zone (DMZ), separating the two Koreas in Gimpo, South Korea, October 5, 2021. REUTERS/Kim Hong-Ji

North Korean soldiers stand guard at their guard post in this picture taken from the top of the Aegibong Peak Observatory, south of the demilitarised zone (DMZ), separating the two Koreas in Gimpo, South Korea, October 5, 2021. REUTERS/Kim Hong-Ji

North Korea's propaganda village Kaepoong is seen in this picture taken from the top of the Aegibong Peak Observatory, south of the demilitarised zone (DMZ), separating the two Koreas in Gimpo, South Korea, October 5, 2021. REUTERS/Kim Hong-Ji

Spiders are seen inside a military fence near the demilitarised zone separating the two Koreas in Paju, South Korea, September 28, 2021. REUTERS/Kim Hong-Ji TPX IMAGES OF THE DAY

Korean Unification flags defaced by strong wind hang on a military fence near the demilitarized zone separating the two Koreas in Paju, South Korea, September 28, 2021. REUTERS/Kim Hong-Ji

Fishermen work in front of a South Korea's observation post near the demilitarized zone separating the two Koreas in Paju, South Korea, September 28, 2021. REUTERS/Kim Hong-Ji

A South Korean soldier walks along a military fence near the demilitarized zone separating the two Koreas in Paju, South Korea, September 28, 2021. REUTERS/Kim Hong-Ji

People look towards the north from an observatory platform near the demilitarized zone separating the two Koreas in Paju, South Korea, September 28, 2021. REUTERS/Kim Hong-Ji

A boy stands in between his parents as they look towards the north through a pair of binoculars near the demilitarized zone separating the two Koreas in Paju, South Korea, September 28, 2021. REUTERS/Kim Hong-Ji

A boy attends a memorial service for their North Korean ancestors, in front of a barbed-wire fence near the demilitarized zone separating the two Koreas, in Paju, South Korea, September 21, 2021. REUTERS/Kim Hong-Ji

A South Korean family prepares a memorial service for their North Korean ancestors, in front of a barbed-wire fence near the demilitarized zone separating the two Koreas, in Paju, South Korea, September 21, 2021. REUTERS/Kim Hong-Ji

A South Korean family bows in the direction of north during a memorial service for their North Korean ancestors, in front of a barbed-wire fence near the demilitarized zone separating the two Koreas, in Paju, South Korea, September 21, 2021. REUTERS/Kim Hong-Ji

A North Korean defector rests after a memorial service for their North Korean ancestors, in front of a barbed-wire fence near the demilitarized zone separating the two Koreas, in Paju, South Korea, September 21, 2021. REUTERS/Kim Hong-Ji

A South Korean family prepares a memorial service for their North Korean ancestors, in front of a barbed-wire fence near the demilitarized zone separating the two Koreas, in Paju, South Korea, September 21, 2021. REUTERS/Kim Hong-Ji

People watch a TV broadcasting file footage of a news report on North Korea firing what appeared to be a pair of ballistic missiles off its east coast, in Seoul, South Korea, September 15, 2021. REUTERS/Kim Hong-Ji

People watch a TV broadcasting file footage of a news report on North Korea firing what appeared to be a pair of ballistic missiles off its east coast, in Seoul, South Korea, September 15, 2021. REUTERS/Kim Hong-Ji

People watch a TV broadcasting file footage of a news report on North Korea firing what appeared to be a pair of ballistic missiles off its east coast, in Seoul, South Korea, September 15, 2021. REUTERS/Kim Hong-Ji

People watch a TV broadcasting file footage of a news report on North Korea firing what appeared to be a pair of ballistic missiles off its east coast, in Seoul, South Korea, September 15, 2021. REUTERS/Kim Hong-Ji

Noh Kyu-duk, Special Representative for Korean Peninsula Peace and Security Affairs at South Korea's Foreign Ministry, attends a trilateral meeting between Japan, U.S., and South Korea, to discuss North Korea, in Tokyo, Japan, September 14, 2021. David Mareuil/Pool via REUTERS

Takehiro Funakoshi, Director-General of the Asian and Oceanian Affairs Bureau at Japan's Foreign Ministry, attends a trilateral meeting between Japan, U.S., and South Korea, to discuss North Korea, in Tokyo, Japan, September 14, 2021. David Mareuil/Pool via REUTERS

Sung Kim, U.S. Special Envoy for North Korea, speaks during trilateral meeting between Japan, U.S., and South Korea, to discuss North Korea, in Tokyo, Japan, September 14, 2021. David Mareuil/Pool via REUTERS

Sung Kim, U.S. Special Envoy for North Korea poses ahead of a trilateral meeting between Japan, U.S., and South Korea, to discuss North Korea, in Tokyo, Japan, September 14, 2021. David Mareuil/Pool via REUTERS

Takehiro Funakoshi, Director-General of the Asian and Oceanian Affairs Bureau at Japan's Foreign Ministry, poses ahead of a trilateral meeting between Japan, U.S., and South Korea, to discuss North Korea, in Tokyo, Japan, September 14, 2021. David Mareuil/Pool via REUTERS

Noh Kyu-duk, Special Representative for Korean Peninsula Peace and Security Affairs at South Korea's Foreign Ministry, poses ahead of a trilateral meeting between Japan, U.S., and South Korea, to discuss North Korea, in Tokyo, Japan, September 14, 2021. David Mareuil/Pool via REUTERS

Takehiro Funakoshi, Director-General of the Asian and Oceanian Affairs Bureau at Japan's Foreign Ministry, poses ahead of a trilateral meeting between Japan, U.S., and South Korea, to discuss North Korea, in Tokyo, Japan, September 14, 2021. David Mareuil/Pool via REUTERS

Sung Kim, U.S. Special Envoy for North Korea, poses ahead of a trilateral meeting between Japan, U.S., and South Korea, to discuss North Korea, in Tokyo, Japan, September 14, 2021. David Mareuil/Pool via REUTERS

Takehiro Funakoshi, Director-General of the Asian and Oceanian Affairs Bureau at Japan's Foreign Ministry, Sung Kim, U.S. Special Envoy for North Korea, and Noh Kyu-duk, Special Representative for Korean Peninsula Peace and Security Affairs at South Korea's Foreign Ministry, attend a trilateral meeting between Japan, U.S., and South Korea, to discuss North Korea, in Tokyo, Japan, September 14, 2021. David Mareuil/Pool via REUTERS

Takehiro Funakoshi, Director-General of the Asian and Oceanian Affairs Bureau at Japan's Foreign Ministry, Sung Kim, U.S. Special Envoy for North Korea, and Noh Kyu-duk, Special Representative for Korean Peninsula Peace and Security Affairs at South Korea's Foreign Ministry, pose ahead of a trilateral meeting between Japan, U.S., and South Korea, to discuss North Korea, in Tokyo, Japan, September 14, 2021. David Mareuil/Pool via REUTERS

North Korea appears to have restarted a nuclear reactor in Yongbyon which has an experimental light water reactor they've been working on that is widely believed to have produced plutonium for nuclear weapons.

Russian Deputy Foreign Minister Igor Morgulov poses for photographs with Noh Kyu-duk, South Korea's Special Representative for Korean Peninsula Peace and Security Affairs before their meeting in Seoul, South Korea, August 24, 2021. REUTERS/Kim Hong-Ji/Pool

Russian Deputy Foreign Minister Igor Morgulov and Noh Kyu-duk, South Korea's Special Representative for Korean Peninsula Peace and Security Affairs attend their meeting in Seoul, South Korea, August 24, 2021. REUTERS/Kim Hong-Ji/Pool

Russian Deputy Foreign Minister Igor Morgulov and Noh Kyu-duk, South Korea's Special Representative for Korean Peninsula Peace and Security Affairs arrive for their meeting in Seoul, South Korea, August 24, 2021. REUTERS/Kim Hong-Ji/Pool

Russian Deputy Foreign Minister Igor Morgulov poses for photographs with Noh Kyu-duk, South Korea's Special Representative for Korean Peninsula Peace and Security Affairs before their meeting in Seoul, South Korea, August 24, 2021. REUTERS/Kim Hong-Ji/Pool

U.S. Special Representative for North Korea, Sung Kim talks with Noh Kyu-duk, South Korea's Special Representative for Korean Peninsula Peace and Security Affairs, during their meeting at Plaza Hotel, in Seoul, South Korea August 23, 2021. Pool via REUTERS/Chung Sung-Jun

U.S. Special Representative for North Korea, Sung Kim talks with Noh Kyu-duk, South Korea's Special Representative for Korean Peninsula Peace and Security Affairs (not in picture), during their meeting at Plaza Hotel, in Seoul, South Korea August 23, 2021. Pool via REUTERS/Chung Sung-Jun

U.S. Special Representative for North Korea, Sung Kim talks to reporters after meeting with Noh Kyu-duk (not in picture), South Korea's Special Representative for Korean Peninsula Peace and Security Affairs, at Plaza Hotel, in Seoul, South Korea August 23, 2021. Pool via REUTERS/Chung Sung-Jun

Special Representative for North Korea, Sung Kim (L) and Noh Kyu-duk (R), South Korea's Special Representative for Korean Peninsula Peace and Security Affairs speak to reporters after their meeting at Plaza Hotel, in Seoul, South Korea August 23, 2021. Pool via REUTERS/Chung Sung-Jun

U.S. Special Representative for North Korea, Sung Kim (L) and Noh Kyu-duk (R), South Korea's Special Representative for Korean Peninsula Peace and Security Affairs leave after speaking to reporters at Plaza Hotel, in Seoul, South Korea August 23, 2021. Pool via REUTERS/Chung Sung-Jun

U.S. Special Representative for North Korea, Sung Kim (L) meets with Noh Kyu-duk (R), South Korea's Special Representative for Korean Peninsula Peace and Security Affairs during their meeting at Plaza Hotell, in Seoul, South Korea August 23, 2021. Pool via REUTERS/Chung Sung-Jun

U.S. Special Representative for North Korea, Sung Kim leaves after talks to reporters at Plaza Hotel, in Seoul, South Korea August 23, 2021. Pool via REUTERS/Chung Sung-Jun

U.S. Special Representative for North Korea, Sung Kim (L) bumps elbows with Noh Kyu-duk (R), South Korea's Special Representative for Korean Peninsula Peace and Security Affairs, during their meeting at Plaza Hotel, in Seoul, South Korea August 23, 2021. Pool via REUTERS/Chung Sung-Jun

U.S. Special Representative for North Korea, Sung Kim (L) bumps elbows with Noh Kyu-duk (R), South Korea's Special Representative for Korean Peninsula Peace and Security Affairs, during their meeting at Plaza Hotel, in Seoul, South Korea August 23, 2021. Pool via REUTERS/Chung Sung-Jun

US Special Representative for North Korea, Sung Kim (center, L) talks with South Korean Unification Minister Lee In-young (center, R) during their meeting to discuss North Korea issues at the unification ministry on June 22, 2021 in Seoul, South Korea. Chung Sung-Jun/Pool via REUTERS

US Special Representative for North Korea, Sung Kim (L) talks with South Korean Unification Minister Lee In-young (R) during their meeting to discuss North Korea issues at the unification ministry on June 22, 2021 in Seoul, South Korea. Chung Sung-Jun/Pool via REUTERS

US Special Representative for North Korea, Sung Kim (L) talks with South Korean Unification Minister Lee In-young (R) during their meeting to discuss North Korea issues at the unification ministry on June 22, 2021 in Seoul, South Korea. Chung Sung-Jun/Pool via REUTERS

US Special Representative for North Korea, Sung Kim (L) attends with South Korean Unification Minister Lee In-young (R) during their meeting to discuss North Korea issues at the unification ministry on June 22, 2021 in Seoul, South Korea. Chung Sung-Jun/Pool via REUTERS

US Special Representative for North Korea, Sung Kim (L) shakes hands with South Korean Unification Minister Lee In-young (R) during their meeting to discuss North Korea issues at the unification ministry on June 22, 2021 in Seoul, South Korea. Chung Sung-Jun/Pool via REUTERS

US Special Representative for North Korea, Sung Kim (L) shakes hands with South Korean Unification Minister Lee In-young (R) during their meeting to discuss North Korea issues at the unification ministry on June 22, 2021 in Seoul, South Korea. Chung Sung-Jun/Pool via REUTERS

US Special Representative for North Korea, Sung Kim (L) shakes hands with South Korean Unification Minister Lee In-young (R) during their meeting to discuss North Korea issues at the unification ministry on June 22, 2021 in Seoul, South Korea. Chung Sung-Jun/Pool via REUTERS

Noh Kyu-duk, South Korea's Special Representative for Korean Peninsula Peace and Security Affairs, poses with Takehiro Funakoshi, Director-General of the Asian and Oceanian Affairs Bureau of the Ministry of Foreign Affairs of Japan, during their bilateral meeting at a hotel in Seoul, South Korea June 21, 2021. Jung Yeon-Je/Pool via REUTERS

Noh Kyu-duk, South Korea's Special Representative for Korean Peninsula Peace and Security Affairs, talks to Takehiro Funakoshi, Director-General of the Asian and Oceanian Affairs Bureau of the Ministry of Foreign Affairs of Japan, during their bilateral meeting at a hotel in Seoul, South Korea June 21, 2021. Jung Yeon-Je/Pool via REUTERS