Donald Trump vs Kim Jong-un: what happens next?

Hours later, Kim branded Trump as "deranged".

He added, "This could probably mean the strongest hydrogen bomb test over the Pacific Ocean".

Kim Jong-un responded via North Korea's state media.

Foreign Minister Ri Yong Ho's threat comes shortly after the country's Supreme Leader Kim Jong-un promised the USA would "pay dearly" for threatening to "totally destroy" North Korea. Like China, North Korea is not a signatory to the 1963 Partial Nuclear Test Ban (PNTB) Treaty.

In his address to the United Nations on Tuesday, President Trump threatened to "totally destroy" North Korea.

Ri's comments came shortly after Kim in a direct statement called Trump "mentally deranged: and said that he would "pay dearly" for his "eccentric" speech".

Secretary of State Rex Tillerson says North Korea's Kim Jong Un is "being tested" by the strongest sanctions ever put in place by the USA and the global community.

It was the first time that a North Korean leader has issued such a direct statement against a U.S. president, dramatically escalating the war of words between the former wartime foes and raising the worldwide nuclear standoff to a new level.

The secretary of state defended Trump's blunt rhetoric in his speech to the U.N. General Assembly in NY on Tuesday, in which the president threatened to "totally destroy" North Korea if the United States is "forced to defend itself or its allies", prompting astonished gasps from some in the audience.

Referring to Trump's Tuesdsay speech at the UN General Assembly, Kim said: "A frightened dog barks louder".

U.S. Secretary of State Rex Tillerson said Friday any U.S. military decision against North Korea in the event of a hydrogen bomb explosion would "ultimately" be up to U.S. President Donald Trump.

In response, Kim issued a statement Thursday, calling Trump's speech "unprecedented rude nonsense" and advising him to "exercise prudence in selecting words". "We really have no choice", he said.

Friday morning, President Trump fired back on Twitter. The country could still get a slot at another time. As per the new penalties', the nations will have to choose whether to do business with the United States or North Korea.

He said: "Action is the best option in treating the dotard who, hard of hearing, is uttering only what he wants to say". He said the order would also allow the U.S. to identify new industries - including textiles, fishing and manufacturing - as potential targets for future actions.