South Korean President Moon Jae-in and his wife Kim Jung-sook arrive at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018. Pyeongyang Press Corps/Pool via REUTERS

South Korean President Moon Jae-in and his wife Kim Jung-sook leave Seoul for Pyongyang, September 18, 2018.

South Korean President Moon Jae-in meets with aides before leaving Seoul for Pyongyang, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

Officials attend an official welcome ceremony for South Korean President Moon Jae-in at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

People attend an official welcome ceremony for South Korean President Moon Jae-in at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in waves from his vehicle after an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in is greeted by North Korean leader Kim Jong Un during an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

A man walks past television screens showing a broadcast at an electronics store in Seoul, South Korea, September 18, 2018, of North Korean leader Kim Jong Un and South Korean President Moon Jae-in in Pyongyang for the inter-Korean summit.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018. Image used for illustrative purpose

South Korean President Moon Jae-in's plane lands at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and his wife Kim Jung-sook leave the Presidential Blue House in Seoul, South Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and North Korean leader Kim Jong Un attend an official welcome ceremony at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.

South Korean President Moon Jae-in and his wife Kim Jung-sook arrive at Pyongyang Sunan International Airport, in Pyongyang, North Korea, September 18, 2018.