U.S. President Donald Trump and North Korean leader Kim Jong Un react at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump and North Korean leader Kim Jong Un react at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

Kim Yo Jong shows a document to her brother, North Korea's leader Kim Jong Un as U.S. Secretary of State Mike Pompeo shows a copy of it to President Donald Trump before they sign them at their summit at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump boards Air Force One after his summit with North Korean leader Kim Jong Un in Singapore June 12, 2018.

U.S. President Donald Trump and North Korea's leader Kim Jong Un smile before their bilateral meeting at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump shakes hands with North Korea's leader Kim Jong Un at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump meets North Korean leader Kim Jong Un at the Capella Hotel on Sentosa island in Singapore June 12, 2018. Kevin Lim/The Straits Times via REUTERS

U.S. President Donald Trump and North Korea's leader Kim Jong Un shake hands during an expanded bilateral meeting at the Capella Hotel on the resort island of Sentosa, Singapore June 12, 2018. With them are Senior North Korean Diplomat Ri Su Yong (top L) and White House Chief of Staff John Kelly (top R).

U.S. President Donald Trump and North Korea's leader Kim Jong Un hold a summit at the Capella Hotel on the resort island of Sentosa, Singapore June 12, 2018.

U.S. President Donald Trump greets North Korean leader Kim Jong Un at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump sits next to North Korea's leader Kim Jong Un before their bilateral meeting at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump gestures after a news conference after his meeting with North Korean leader Kim Jong Un at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

A TV screen shows a news report about the meeting between U.S. President Donald Trump and North Korea's leader Kim Jong Un at a media center for the summit, in Singapore June 12, 2018.

The motorcade of U.S. President Donald Trump leaves Sentosa island, Singapore June 12, 2018.

U.S. President Donald Trump walks with North Korean leader Kim Jong Un at the Capella Hotel on Sentosa island in Singapore June 12, 2018. Kevin Lim/The Straits Times via REUTERS

U.S. President Donald Trump speaks during a news conference after his meeting with North Korean leader Kim Jong Un at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump shakes hands with North Korean leader Kim Jong Un at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump and North Korea's leader Kim Jong Un meet at the Capella Hotel on the resort island of Sentosa, Singapore June 12, 2018.

U.S. President Donald Trump and North Korean leader Kim Jong Un walk to shake hands at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump speaks with North Korea's leader Kim Jong Un before their expanded bilateral meeting at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump meets North Korean leader Kim Jong Un at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump gestures next to North Korea's leader Kim Jong Un before their bilateral meeting at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump walks with North Korean leader Kim Jong Un at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

U.S. President Donald Trump and North Korean leader Kim Jong Un react at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

North Korea's leader Kim Jong Un looks at U.S. President Donald Trump before their bilateral meeting at the Capella Hotel on Sentosa island in Singapore June 12, 2018.

North Korean defector Justin Kim (R), now a student in New York State, watches replays of President Donald Trump's summit meeting in Singapore with North Korea's Kim Jung Un on television, at a motel in Leesburg, Virginia, U.S., June 11, 2018.

U.S. President Donald Trump shows the document, that he and North Korea's leader Kim Jong Un signed acknowledging the progress of the talks and pledge to keep momentum going, after their summit at the Capella Hotel on Sentosa island in Singapore June 12, 2018.