The Central Committee and the Central Military Commission of the Workers' Party of Korea hold a banquet at the Mokran House in celebration of the second successful test-fire of ICBM Hwasong-14, in this photo released July 30, 2017.

Kim Jong Un reacts with scientists and technicians of the DPRK Academy of Defence Science after the test-launch of the intercontinental ballistic missile Hwasong-14, in this photo released July 5, 2017.

People watch a huge screen showing the test launch of intercontinental ballistic missile Hwasong-14, in this photo released July 5, 2017.

Members who contributed to the success of the ICBM Hwasong-14 test launch arrive in Pyongyang, in this photo released July 7, 2017.

Kim Jong Un guides the second test-fire of ICBM Hwasong-14, in this photo released July 29, 2017.

Kim Jong Un watches the launch of a Hwasong-12 missile in this undated photo released September 16, 2017.

The intercontinental ballistic missile Hwasong-14, in this photo released July 4, 2017.

Kim Jong Un looks on during a visit to the Chemical Material Institute of the Academy of Defense Science in this undated photo released August 23, 2017.

Army personnel and people gather at Kim Il Sung Square in Pyongyang to celebrate the successful test-launch of ICBM Hwasong-14, July 6, 2017.

Kim Jong Un reacts during a celebration for nuclear scientists and engineers who contributed to a hydrogen bomb test, in this undated photo released September 10, 2017.

Kim Jong Un inspects the ICBM Hwasong-14 in this undated photo released by July 5, 2017.

Image used for illustrative purpose. The intercontinental ballistic missile Hwasong-14 is seen during its test, in this photo released July 5, 2017. Reuters/KCNA KCNA

Members who contributed to the success of the ICBM Hwasong-14 test launch arrive in Pyongyang, in this photo released July 7, 2017.

A Hwasong-12 missile is launched in this undated combination photo released September 16, 2017.

Army personnel and people gather at Kim Il Sung Square in Pyongyang July 6, 2017 to celebrate the successful test-launch of intercontinental ballistic rocket Hwasong-14.

A woman walks past a large TV screen showing news about North Korea's missile launch in Tokyo, Japan, August 29, 2017.

Kim Jong Un guides the underwater test-fire of a strategic submarine ballistic missile, in this photo released April 24, 2016.

Intercontinental ballistic missile (ICBM) Hwasong-14 is pictured during its second test-fire, in this photo released July 29, 2017.

Ko Yun-hwa (L), Administrator of Korea Meteorological Administration, points at where seismic waves observed in South Korea came from, during a media briefing at Korea Meteorological Administration in Seoul, South Korea, January 6, 2016.