DONALD Trump 'is to order a military strike against North Korea within a year' after Kim Jong-un's military boasted it had fired a ballistic missile capable of hitting the US.

Senior military sources in Washington have reportedly claimed Pentagon officials have laid out plans to obliterate a nuclear weapons facility operating deep within a mountain range inside the rogue state.

The news comes hours after the US flew two supersonic bombers over the Korean Peninsula  in a show of force against North Korea.

The B-1 bombers were escorted by South Korean fighter jets as they performed a low-pass over an air base near the South Korean capital of Seoul before returning to the Andersen Air Force Base in Guam.

The US Air Force said the mission was a response to consecutive ICBM tests by Kim this month.

Analysts say flight data from the second test conducted Friday night showed that a broader part of mainland America, including Los Angeles and Chicago, is now in range of Pyongyang's weapons.