North Korea’s Foreign Minister said on Saturday that United States President Donald Trump’s vow to “totally destroy” the country if necessary had made “our rockets’ visit to the entire US mainland all the more inevitable”.

Ri Yong-ho’s remarks at the United Nations General Assembly came hours after US Air Force B-1B Lancer bombers escorted by F-15C Eagle fighter escorts flew in international airspace over the waters east of North Korea, according to Reuters.

The Pentagon said the flight flew the farthest north of the demilitarised zone separating North and South Korea that any US fighter jet or bomber has flown in the 21st century, and demonstrated the range of military options available to Trump, according to the report.

Ri Yong-Ho called Trump a “mentally deranged person full of megalomania”, whose threats had increased the chances of military confrontation, AFP reported. He said the US leader who “holds the nuclear button” posed “the gravest threat to international peace and security today.”

Last week, in his first address to the General Assembly, Trump called leader Kim Jong-Un a “Rocket Man” on a “suicide mission,” prompting Kim to warn in turn that the US president would “pay dearly” for his threat.

Ri called the United States-led resolution that imposed sanctions on North Korea unjustified, and said Pyongyang was left with no other choice but to respond with the “nuclear hammer of justice.” He said North Korea’s nuclear drive was aimed at developing a “war deterrent” and that his country was a “responsible nuclear weapon state.”

The North Korean threat has dominated this year’s gathering of world leaders at the United Nations, amid fears that the heated rhetoric could trigger a war.