The BBC's John Sudworth, in Pyongyang, explains what may happen next;
A North Korean missile has detonated soon after launch, South Korean and US military officials have said, a day after Pyongyang warned the US amid rising tension in the region.
The US said a ballistic missile exploded within seconds of launch.
Hours earlier, North Korea paraded what appeared to be long-range ballistic missiles at a major military display.
It has already conducted five nuclear tests and a series of missile launches in contravention of UN resolutions.
The latest development came as US Vice-President Mike Pence arrived in the South Korean capital, Seoul, where he was expected to discuss the best way to deal with North Korea's missile and nuclear programmes.