Kim Jong Un's New Year message: Nuclear North a reality, not a threat

North Korean leader Kim Jong Un speaks during a conference of cell chairpersons of the ruling party in Pyongyang. Photo / AP

North Korean leader Kim Jong Un says the United States will never be able to start a war against the north now that his country has developed the capability to hit all of the US mainland with its nuclear weapons.

"The entire United States is within range of our nuclear weapons, and a nuclear button is always on my desk. This is reality, not a threat," Kim said during a televised New Year's Day speech.

The North Korean leader said the country had achieved the historic feat of "completing" its nuclear forces and added that he has a "nuclear button" on his desk.

The customary New Year's address was broadcast Monday morning on North Korean state television.

North Korean leader Kim Jong Un says the United States should be aware that his country's nuclear forces are now a reality, not a threat. Photo / AP

"This year we should focus on mass producing nuclear warheads and ballistic missiles for operational deployment," Kim said.

"These weapons will be used only if our security is threatened."

The speech is being watched closely, as Kim followed up on promises he made during his 2017 New Year's Day address, when he vowed to speed up the country's nuclear weapons development.

Kim touted last year that North Korea had "entered the final stage of preparation" to test an intercontinental ballistic missile. North Korea's 15 ballistic missile tests of 2017 focused on intermediate and long-range rockets.

Kim is also believed to have called for the mass-production of nuclear weapons and missiles and is "putting them into service", according to South Korean news agency Yonhap.

North Korea tested intercontinental ballistic missiles and conducted its sixth and most powerful nuclear test in September in defiance of international warnings and sanctions, raising fears of a new conflict on the Korean peninsula.

North Koreans watch as fireworks explode as part of New Year celebrations, above the Taedong River as viewed from Kim Il Sung Square, in Pyongyang. Photo / AP