South Korea's President Moon Jae-in and Singapore's Prime Minister Lee Hsien Loong shake hands during a press conference at the Istana Presidential Palace in Singapore, 12 July 2018. Wallace Woon/Pool via REUTERS

South Korea's President Moon Jae-in speaks during a press conference alongside Singapore's Prime Minister Lee Hsien Loong (not pictured) at the Istana Presidential Palace in Singapore, 12 July 2018. Wallace Woon/Pool via REUTERS

South Korea's President Moon Jae-in and Foreign Minister Kang Kyung-wha attend a meeting with Singapore's Prime Minister Lee Hsien Loong during a visit at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South Korea's President Moon Jae-in and Singapore's Prime Minister Lee Hsien Loong attend a meeting alongside their delegations at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South Korea's President Moon Jae-in shakes hands with Singapore's Prime Minister Lee Hsien Loong during a visit at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South Korea's President Moon Jae-in shakes hands with Singapore's Prime Minister Lee Hsien Loong during a visit at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South Korea's President Moon Jae-in shakes hands with Singapore's Prime Minister Lee Hsien Loong during a visit at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South Korea's President Moon Jae-in shakes hands with Singapore's Prime Minister Lee Hsien Loong during a visit at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South Korea President Moon Jae-in (L) and Singapore Prime Minister Lee Hsien Loong (R) are pictured during a press conference at the Istana Presidential Palace in Singapore, 12 July 2018. Wallace Woon/Pool via REUTERS

South KoreaÕs President Moon Jae-in and Foreign Minister Kang Kyung-wha attend a meeting with SingaporeÕs Prime Minister Lee Hsien Loong during a visit at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South KoreaÕs President Moon Jae-in and SingaporeÕs Prime Minister Lee Hsien Loong attend a meeting alongside their delegations at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South KoreaÕs President Moon Jae-in shakes hands with SingaporeÕs Prime Minister Lee Hsien Loong during a visit at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South KoreaÕs President Moon Jae-in shakes hands with SingaporeÕs Prime Minister Lee Hsien Loong during a visit at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South KoreaÕs President Moon Jae-in shakes hands with SingaporeÕs Prime Minister Lee Hsien Loong during a visit at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South KoreaÕs President Moon Jae-in shakes hands with SingaporeÕs Prime Minister Lee Hsien Loong during a visit at the Istana in Singapore July 12, 2018. Wallace Woon/Pool via REUTERS

South Korean Lee Dong-woon (2nd R), 84, who was originally from North Korea's Songhwa in Hwanghae Province, bows with his son and grandson (R) in the direction of the North during a memorial service for ancestors near the demilitarized zone separating the two Koreas, in Paju, 55 km (34 miles) north of Seoul February 10, 2013, on the occasion of Seolnal, the Korean Lunar New Year's day. Lee has not been able to visit his hometown since the 1950-53 Korean War. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: MILITARY POLITICS SOCIETY)

South Korean Lee Dong-woon (2nd R), 84, who was originally from North Korea's Songhwa in Hwanghae Province, bows with his son and grandson (R) in the direction of the North during a memorial service for ancestors near the demilitarized zone separating the two Koreas, in Paju, 55 km (34 miles) north of Seoul February 10, 2013, on the occasion of Seolnal, the Korean Lunar New Year's day. Lee has not been able to visit his hometown since the 1950-53 Korean War. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: MILITARY POLITICS SOCIETY)

South Korean Lee Dong-woon (L), 82, who was originally from North Korea's Songhwa in Hwanghae Province, and his son bow in the direction of the North during a memorial service for ancestors at Imjingak pavilion in Paju, north of Seoul September 12, 2011, on the occasion of Chuseok, the Korean thanksgiving day. Lee has not been able to visit his hometown since the 1950-53 Korean War. The Chuseok is a time for Korean families to remember and honour their dead ancestors and Imjingak pavilion is the closest residents of the capitalist South can get to the border with the communist North. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: SOCIETY)

South Korean Lee Dong-woon (L), 82, who was originally from North Korea's Songhwa in Hwanghae Province, and his family members bow in the direction of the North during a memorial service for ancestors at Imjingak pavilion in Paju, north of Seoul September 12, 2011, on the occasion of Chuseok, the Korean thanksgiving day. Lee has not been able to visit his hometown since the 1950-53 Korean War. The Chuseok is a time for Korean families to remember and honour their dead ancestors and Imjingak pavilion is the closest residents of the capitalist South can get to the border with the communist North. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: SOCIETY)

South Korean Lee Dong-woon (2nd R), 82, who was originally from North Korea's Songhwa in Hwanghae Province, and his family members bow in the direction of the North during a memorial service for ancestors at Imjingak pavilion in Paju, north of Seoul February 3, 2011, on the occasion of Seolnal, the Korean lunar new year day. Lee has not been able to visit his hometown since the 1950-53 Korean War. The Seolnal is also a time for Korean families to remember and honour their dead ancestors and Imjingak pavilion is the closest residents of the capitalist south can get to the border with the communist north. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: MILITARY SOCIETY)

Nigeria's Peter Osaze Odemwingie (C) scores a goal against South Korea's goalkeeper Lee Woon-jae during their friendly soccer match in Suwon, south of Seoul, August 11, 2010. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: SPORT SOCCER)

South Korea's goalkeeper Lee Woon-jae reacts at the end of a 2010 World Cup second round match against Uruguay in Port Elizabeth June 26, 2010. REUTERS/Paul Hanna (SOUTH AFRICA - Tags: SPORT SOCCER WORLD CUP)

South Korea's Park Chu-young (bottom), Lee Young-pyo (R) and goalkeeper Lee Woon-jae play foot volleyball during a soccer training session in Rustenburg June 19, 2010. South Korea is playing in Group B at the World Cup. REUTERS/Lee Jae-Won (SOUTH AFRICA - Tags: SPORT SOCCER WORLD CUP)

South Korea's goalkeeper Lee Woon-jae answers a reporter's question at Hunters Rest hotel in Rustenburg June 14, 2010. REUTERS/Lee Jae-Won (SOUTH AFRICA - Tags: SPORT SOCCER WORLD CUP)

South Korea's goalkeeper Lee Woon-jae (R) leaves after attending an interview with the media at Hunters Rest hotel in Rustenburg June 14, 2010. REUTERS/Lee Jae-Won (SOUTH AFRICA - Tags: SPORT SOCCER WORLD CUP)

South Korea's national soccer player Lee Woon-Jae (R) looks on during a training session in Neustift May 26, 2010. REUTERS/Dominic Ebenbichler (AUSTRIA - Tags: SPORT SOCCER WORLD CUP)

South Korea's national soccer player Lee Woon-Jae practices during a training session in Neustift May 26, 2010. REUTERS/Dominic Ebenbichler (AUSTRIA - Tags: SPORT SOCCER WORLD CUP)

South Korea's national soccer player Lee Woon-Jae practices during a training session in Neustift May 26, 2010. REUTERS/Dominic Ebenbichler (AUSTRIA - Tags: SPORT SOCCER WORLD CUP)

South Korea's Lee Woon-jae poses before a training session in Paju, north of Seoul May 19, 2010. Picture taken May 19, 2010. REUTERS/Truth Leem (SOUTH KOREA - Tags: SPORT SOCCER WORLD CUP 2010 PREVIEW - HEADSHOT)

South Korea's Lee Woon-jae stands before a friendly soccer match at the Seoul World Cup stadium in Seoul May 16, 2010. REUTERS/Jo Yong-Hak (SOUTH KOREA - Tags: SPORT SOCCER WORLD CUP 2010 PREVIEW - HEADSHOT)

Principal Gwak Jong-woon (L) gives diplomas to high school graduates who escaped from North Korea during a graduation ceremony at Hangyeore High School, which was built to educate North Korean teenage defectors, in Anseong, about 80 km (50 miles) south of Seoul February 10, 2010. Forty-six students graduated from the high school on Wednesday and will go on to college or get employment. REUTERS/Lee Jae-Won (SOUTH KOREA - Tags: EDUCATION POLITICS)

South Korea's goalkeeper Lee Woon-Jae dives for the ball during a training session before a friendly match against Finland at Ciudad de Malaga stadium in Malaga, southern Spain January 18, 2010. REUTERS/Jon Nazca (SPAIN - Tags: SPORT SOCCER IMAGES OF THE DAY)

(L-R, front row) South Korea's Ki Sung-yueng, Lee Geun-ho, Lee Young-pyo, Lee Chung-yong, Park Ji-sung, (L-R second row) Cho Yong-hyung, Cha Du-ri, Park Chu-young, Lee Jung-soo, Kim Jung-woo and Lee Woon-jae pose before their international friendly soccer match against Senegal at Seoul World Cup stadium October 14, 2009. REUTERS/Choi Bu-Seok (SOUTH KOREA SPORT SOCCER)

South Korea's national soccer team pose before their friendly soccer match against Australia in Seoul September 5, 2009. (L-R, back row) Lee Woon-jae, Ki Sung-yueng, Kim Jung-woo, Kim Dong-jin, Lee Jung-soo and Lee Dong-gook. (L-R, front row) Cho Yong-hyung, Park Chu-young, Lee Chung-yong, Lee Young-pyo and Park Ji-sung. REUTERS/Choi Bu-Seok (SOUTH KOREA SPORT SOCCER)

Australia's Joshua Kennedy (C) fights for the ball against South Korea's goalkeeper Lee Woon-jae (L) and Lee Jung-soo during their friendly soccer match in Seoul September 5, 2009. REUTERS/Jo Yong-Hak (SOUTH KOREA SPORT SOCCER)

Australia's Patrick Kisnorbo (C) scores past South Korea's goalkeeper Lee Woon-jae (L) next to teammate Scott Mcdonald (R) during their friendly soccer match in Seoul September 5, 2009. REUTERS/Jo Yong-Hak (SOUTH KOREA SPORT SOCCER)

South Korea's national soccer team players pose for a photograph before their 2010 World Cup qualifying soccer match against North Korea in Seoul April 1, 2009. (L to R, back row) Lee Woon-jae, Kang Min-soo, Hwang Jae-won, Park Chu-young, Cho Won-hee and Ki Sung-yeung. (L to R, front row) Park Ji-sung, Oh Beom-seok, Lee Keun-ho, Lee Chung-yong and Lee Young-pyo. REUTERS/Jo Yong-Hak (SOUTH KOREA SPORT SOCCER)

South Korea's (L to R) Park Chu-young, Park Ji-sung, Lee Woon-jae, Cho Won-hee and Kang Min-soo greet fans after their victory over North Korea at the 2010 World Cup qualifying soccer match in Seoul April 1, 2009. REUTERS/Jo Yong-Hak (SOUTH KOREA SPORT SOCCER)

South Korea's national soccer team players pose for a photograph before their friendly soccer match against Iraq in Suwon, south of Seoul, March 28, 2009. (L to R in the back row) Lee Woon-jae, Park Chu-young, Ki Sung-yeung, Kang Min-soo, Oh Beom-seok and Hwang Jae-won. (L to R in the front row) Lee Young-pyo, Park Ji-sung, Lee Chung-yong, Lee Keun-ho and Cho Won-hee. REUTERS/Jo Yong-Hak (SOUTH KOREA SPORT SOCCER)

Members of the South Korea national soccer team pose for a group photo before their World Cup 2010 qualifying soccer match against Iran in Tehran February 11, 2009. The players are (bottom L-R) Park Ji Sung, Lee Young Pyo, Lee Keun Ho, Cho Yong Hyung, Kang Minsoo, (top L-R) Jeong Shung Hoon, Lee Woon Jae, Ki Sung Yueng, Lee Chung Yong, Kim Jung Woo and Oh Beom Seok. REUTERS/Morteza Nikoubazl (IRAN)

Lee Dong-woon (C), 80, who was originally from North Korea and has not visited his hometown since the 1950-53 Korean War, holds a memorial service for the ancestors in the North with his son and grandson (L) at Imjingak in Paju, about 52 km (32 miles) north of Seoul January 26, 2009. The memorial was held near the demilitarized zone separating the two Koreas and is the closest they can get to the North's border. The offering was made during the Korean holiday period of "Seol" or the lunar new year which is also a time for Korean families to remember and honour their dead ancestors. Millions of South Koreans visit their native places during the "Seol", the Korean lunar new year holiday celebrated on January 25-27. REUTERS/Lee Jae-Won (SOUTH KOREA)

Lee Dong-woon (C), 80, who was originally from North Korea and has not visited his hometown since the 1950-53 Korean War, holds a memorial service for the ancestors in the North with his son and grandson (bottom) at Imjingak in Paju, about 52 km (32 miles) north of Seoul January 26, 2009. The memorial was held near the demilitarized zone separating the two Koreas and is the closest they can get to the North's border. The offering was made during the Korean holiday period of "Seol" or the lunar new year which is also a time for Korean families to remember and honour their dead ancestors. Millions of South Koreans visit their native places during the "Seol", the Korean lunar new year holiday celebrated on January 25-27. REUTERS/Lee Jae-Won (SOUTH KOREA)

Lee Dong-woon (L), 80, who was originally from North Korea and has not visited his hometown since the 1950-53 Korean War, holds a memorial service for the ancestors in the North at Imjingak in Paju, about 52 km (32 miles) north of Seoul January 26, 2009. The memorial was held near the demilitarized zone separating the two Koreas and is the closest they can get to the North's border. The offering was made during the Korean holiday period of "Seol" or the lunar new year which is also a time for Korean families to remember and honour their dead ancestors. Millions of South Koreans visit their native places during the "Seol", the Korean lunar new year holiday celebrated on January 25-27. REUTERS/Lee Jae-Won (SOUTH KOREA)

South Korea's goalkeeper Lee Woon-jae controls the ball during a soccer training session in Doha November 12, 2008. South Korea will play a friendly soccer match against Qatar on November 14, and a World Cup 2010 Qualifying - Asia match against Saudi Arabia on November 19. REUTERS/Fadi Al-Assaad (QATAR)

South Korea's Trade Minister Kim Jong-hoon (R) bows next to Agriculture Minister Chung Woon-chun during a news conference at the Integrated Government Building in Seoul June 26, 2008. South Korea will allow the resumption of U.S. beef imports starting Thursday, the farm ministry said, implementing an unpopular deal that sparked street protests and caused a crisis for the government. REUTERS/Lee Jae-Won (SOUTH KOREA)

(L-R) South Korean Prime Minister Han Seung-soo, Agriculture Minister Chung Woon-chun and Trade Minister Kim Jong-hoon bow during a news conference at the Integrated Government Building in Seoul June 26, 2008. South Korea will allow the resumption of U.S. beef imports starting Thursday, the farm ministry said, implementing an unpopular deal that sparked street protests and caused a crisis for the government. REUTERS/Lee Jae-Won (SOUTH KOREA)

(L-R) South Korean Prime Minister Han Seung-soo, Agriculture Minister Chung Woon-chun and Trade Minister Kim Jong-hoon bow during a news conference at the Integrated Government Building in Seoul June 26, 2008. South Korea will allow the resumption of U.S. beef imports starting Thursday, the farm ministry said, implementing an unpopular deal that sparked street protests and caused a crisis for the government. REUTERS/Lee Jae-Won (SOUTH KOREA)

Agriculture Minister Chung Woon-chun (C) is escorted by his bodyguards as protesters and photographers approach him during a candlelight vigil on a street leading to the U.S. Embassy and the presidential Blue House in central Seoul June 10, 2008. The minister appeared at the rally to speak but had to leave without delivering his speech, triggering anger from protesters. About one million people fearing infection by mad cow disease across the country demonstrated Tuesday evening to the demand full-scale renegotiation of a beef deal with the U.S. and the resignation of President Lee Myung-bak as they commemorated the historic June 10 mass pro-democracy demonstrations in 1987. REUTERS/Lee Jae-Won (SOUTH KOREA)

South Korean dog breeder Lee Ki-woon walks a North Korean breed named "poongsan" at the Mount Kumgang resort in North Korea February 16, 2008. Lee is one of the few South Koreans who breeds poongsan and he took two of his dogs across the border to compete in the first dog sled race held in North Korea. Picture taken February 16, 2008. REUTERS/Lee Jae-Won (NORTH KOREA)

South Korean dog breeder Lee Ki-woon walks a North Korean breed named "poongsan" at the Mount Kumgang resort in North Korea February 16, 2008. Lee is one of the few South Koreans who breeds poongsan and he took two of his dogs across the border to compete in the first dog sled race held in North Korea. Picture taken February 16, 2008. REUTERS/Lee Jae-Won (NORTH KOREA)

South Korean dog breeder Lee Ki-woon walks a North Korean breed named Poongsan at the Mount Kumgang resort February 16, 2008. Lee is one of the few South Koreans who breeds Poongsan and took two of his dogs across the border to compete in the first dog sled race held in North Korea. Picture taken February 16, 2008. REUTERS/Lee Jae-Won (NORTH KOREA)

South Korean dog breeder Lee Ki-woon walks a North Korean breed named poongsan at the Mount Kumgang resort in North Korea February 16, 2008. Lee is one of the few South Koreans who breeds poongsans and he took two of his dogs across the border to compete in the first dog sled race held in North Korea. Picture taken February 16, 2008. REUTERS/Lee Jae-Won (NORTH KOREA)

Japan's goalkeeper Yoshikatsu Kawaguchi (L) watches South Korea's players celebrate with goalkeeper Lee Woon-jae (hidden) after he saved Japan's Naotake Hanyu's last penalty kick to win the game during their 2007 AFC Asian Cup 3rd/4th placing soccer match at the Jaka Baring stadium in Palembang July 28, 2007. REUTERS/Lee Jae-Won (INDONESIA)

South Korea's soccer players celebrate with goalkeeper Lee Woon-jae (bottom) after Lee saved a penalty shot to help the team win against Japan during their 3rd/4th placing match at the 2007 AFC Asian Cup soccer tournament at Jaka Baring Stadium in Palembang July 28, 2007. REUTERS/Lee Jae-Won (INDONESIA)

South Korea's players celebrate with goalkeeper Lee Woon-jae (hidden) after he saved Japan's Naotake Hanyu's last penalty kick to win the game during their 2007 AFC Asian Cup 3rd/4th placing soccer match at the Jaka Baring stadium in Palembang July 28, 2007. REUTERS/Lee Jae-Won (INDONESIA)

South Korea's Lee Woon-jae reacts after saving Japan's Naotake Hanyu's last penalty kick to give them the win, during the 2007 AFC Asian Cup 3rd/4th placing soccer match at the Jaka Baring stadium in Palembang July 28, 2007. REUTERS/Lee Jae-Won (INDONESIA)

South Korea's players celebrate with goalkeeper Lee Woon-jae (1) after he saved Japan's Naotake Hanyu's last penalty kick to win the game during their 2007 AFC Asian Cup 3rd/4th placing soccer match at the Jaka Baring stadium in Palembang July 28, 2007. REUTERS/Kim Kyung-Hoon (INDONESIA)

South Korea's Lee Woon-jae dives for the ball during the 2007 AFC Asian Cup 3rd/4th placing soccer match between Japan and South Korea at the Jaka Baring stadium in Palembang July 28, 2007. REUTERS/Lee Jae-Won (INDONESIA)

Japan's Hisato Sato (11) consoles Naotake Hanyu (on ground) after Hanyu missed the last penalty kick during the 2007 AFC Asian Cup 3rd/4th placing soccer match between Japan and South Korea at the Jaka Baring stadium in Palembang July 28, 2007. South Korea's goalkeeper Lee Woon-jae saved Hanyu's kick to win the game. Behind Sato is Kisho Yano. REUTERS/Kim Kyung-Hoon (INDONESIA)

South Korea's players celebrate with goalkeeper Lee Woon-jae (1) after he saved Japan's Naotake Hanyu's last penalty kick to win the game during their 2007 AFC Asian Cup 3rd/4th placing soccer match at the Jaka Baring stadium in Palembang July 28, 2007. REUTERS/Kim Kyung-Hoon (INDONESIA)