Tillerson says no 'imminent threat' from North Korea

North Korean missile launch

North Korea "should cease any consideration of actions that will lead to the end of the regime and destruction of its people", Mattis said in a statement.

Britain's UN ambassador said the United Kingdom "stands shoulder to shoulder with the United States" in tackling the nuclear threat from North Korea and making sure it can not pursue its nuclear and ballistic missile programmes. Furthermore, it should "cease any consideration of actions that would lead to the end of its regime and the destruction of its people", he said.

It comes following an exchange of threats and boasts of nuclear power by President Donald Trump and North Korea.

The warning came soon after The Washington Post reported the North has successfully miniaturized a nuclear warhead to fit atop its missiles.

Mattis said that though the State Department is making efforts to resolve the threat using diplomatic means, allied militaries possess "robust defensive and offensive capabilities".

"Mattis warned North Korean dictator Kim Jong Un to take heed of the United Nations Security Council's unified voice, and statements from governments the world over, who agree [North Korea] poses a threat to global security and stability".

"The DPRK regime's actions will continue to be grossly overmatched by ours and would lose any arms race or conflict it initiates", said the USA defence secretary.

On July 28, North Korea launched its second ICBM, which had the longest flight of a ballistic missile in the country's history, the Pentagon confirmed. Shortly before Trump's remarks on the nuclear arsenal, Tillerson landed in Guam for a previously scheduled visit after telling reporters he did not believe there was an imminent threat from North Korea and that "Americans should sleep well at night".

The warning followed Trump's tweets earlier in the day that the USA nuclear arsenal is "now far stronger and more powerful than ever before".

President Trump on Wednesday declared the USA nuclear arsenal "far stronger and more powerful than ever before" even as his top diplomat was working to calm the North Korea crisis and insisting there wasn't "any imminent threat". Democratic leaders criticised Trump for his statement on North Korea.

Asked whether Mr Trump's escalating rhetoric was hurting prospects for reviving negotiations, Mr Rycroft said: "What's hurting the six-party talks is the inability so far of the North Korean regime to do what it has to do which is to halt its nuclear programme and to halt its intercontinental ballistic missile programme". It says its ICBMs are a legitimate means of defense against perceived USA hostility, including joint military drills with South Korea.