INTERNATIONAL: North Korea will continue to develop "formidable striking capabilities" that cannot be bartered or sold for anything, leader Kim Jong Un has said, according to state media on Monday, as he visited workers involved with the country's biggest missile test.

Kim was meeting with officials, scientists, technicians and workers who contributed to a missile launch on Thursday, which North Korea has said was its largest intercontinental ballistic missile (ICBM).

"Only when one is equipped with the formidable striking capabilities, overwhelming military power that cannot be stopped by anyone, one can prevent a war, guarantee the security of the country and contain and put under control all threats and blackmails by the imperialists," Kim has said.

While personally overseeing the test on Thursday, Kim has also mentioned that the new ICBM was to help deter any military moves by the United States, which remains technically at war with the North after the 1950-1953 Korean War ended in an armistice rather than a peace agreement.

Washington has sought to pressure Pyongyang into surrendering or reducing its arsenal of nuclear weapons and ICBMs, which may be able to strike targets in the United States.

But Kim has said his self-defence force "cannot be bartered nor be bought with anything" and will be held firm without the slightest vacillation despite harsh trials and difficulties.

North Korea will continue to build a "more perfect and stronger strategic force," Kim has said, referring to the country's nuclear force.

The United States has said on Friday it will push United Nations sanctions on North Korea to be strengthened over "increasingly dangerous provocations," but China and Russia have signaled opposition and instead argued for such measures to be eased.

North Korea has said Thursday's missile was the Hwasong-17, and Japan and South Korea have confirmed that flight data has showed the launch flew higher and longer than any previous North Korean test.