A North Korean envoy to the UN told Reuters the country is "not afraid" of a potential ramping up of sanctions by the US.

Choe Myong Nam said North Korea would continue with the "full acceleration of the nuclear programs and missiles programs" amid "hostile activities" by the US and South Korea.

Last week Secretary of State Tillerson said the US considered pre-emptive military action against Pyongyang "an option" and called the country's nuclear program an "imminent" threat.