North Korean Minister of Foreign Affairs Ri Yong Ho said Pyongyang could respond to Donald Trump’s threats of military action by testing a hydrogen bomb in the Pacific Ocean, according to South Korean news agency Yonhap.

“It could be the most powerful detonation of an H-bomb in the Pacific,” he told reporters in New York, adding that he did not know what actions could be taken as it would be ordered by North Korean leader Kim Jong-Un. Ri is due to address the United Nations General Assembly this weekend.

Just hours earlier, Kim had called United States President Donald Trump “mentally deranged”, and had promised to make him pay for threatening North Korea, the official Korean Central News Agency reported.

“Action is the best option in treating the dotard who, hard of hearing, is uttering only what he wants to say,” Kim Jong-un said referring to Trump. “As a man representing the Democratic People’s Republic of Korea and on behalf of the dignity and honour of my state and people and on my own, I will make the man holding the prerogative of the supreme command in the United States pay dearly for his speech calling for totally destroying us.” The North Korean leader added that he would “surely and definitely tame the mentally deranged US dotard with fire”.

Soon, the US president hit back at Kim Jong-un. “Kim Jong-un of North Korea, who is obviously a madman who doesn’t mind starving or killing his people, will be tested like never before!” Trump said on Twitter. He, however, did not clarify what he meant by testing.

On September 19, Trump had said at the United Nations General Assembly that he would be forced to destroy North Korea if the United States is forced to defend itself.

Trump also issued an executive order on Thursday to ban firms from operating in the United States if they deal with North Korea. “Foreign financial institutions are now on notice that going forward they can choose to do business with the United States or with North Korea, but not both,” US Treasury Secretary Steven Mnuchin was quoted as saying.

Tension on the Korean peninsula has escalated as the North has stepped up the development of weapons, testing a string of missiles this year. North Korean state media had on September 3 claimed that they had successfully conducted a hydrogen bomb test. This was the country’s sixth underground nuclear test since 2006.