North Korea-US war 'inevitable' if Kim Jong-un gets missiles that can target US cities, warns defence expert

'It is now more likely than ever that President Trump will have to make good on his threat to "utterly destroy" a nation of 25 million people'

Professor DeThomas said Donald Trump’s recent speech to the UN General Assembly “may have closed any remaining doors to a diplomatic resolution” with Kim Jong-Un (AP)

Nuclear war between North Korea and the US will be “inevitable” if Kim Jong-un develops missiles that can target US cities, a leading expert has said.

Professor Joseph DeThomas, former American ambassador who spent 32 years in the US state department, warned the US has “psychologically manoeuvered” itself to believe it “cannot live for a day” under the threat of a single North Korean nuclear weapon capable of reaching major US cities.

Writing on 38 North, a website featuring analysis of events in and around North Korea, Professor DeThomas added Donald Trump’s recent speech to the UN General Assembly “may have closed any remaining doors to a diplomatic resolution”.

He said the President’s speech and the North Korean reaction seem to have set the US on a path that could “very well end in a major war in Asia”.

The Pennsylvania State University professor writes that the escalating threats and "closing off" of diplomatic options by both sides makes it now "more likely than ever" President Trump would have to make good on his threat to "utterly destroy" a nation of 25 million people.

Fleshing out his analysis, Professor DeThomas writes: “Both sides seem to have manoeuvered themselves psychologically into the belief that war is inevitable unless the other side capitulates to its desired end state.

“For the DPRK this means that safety can only be achieved if it can target US cities. For the US it means war is inevitable if the DPRK achieves that goal.”

He adds the US administration is likely to have a military plan in place if Pyongyang develops weapons able to target the US, amid concern that the country “cannot live for a day” under this threat.

“Senior US administration officials have already made numerous comments about preventive war. They have begun the usual US psychological preparation for conflict by labelling the prospective opponent evil and mad,” he wrote.

“And they have given indications that they have agreed on military options that will be brought into play under certain publicly ill-defined circumstances.

“It is likely the inner councils of the administration have already agreed on a set of military actions that will be put into play if Pyongyang is about to field a nuclear-armed missile capable of striking the continental United States before sanctions bring Pyongyang to its knees.

“This unspoken decision stems from the belief that the United States cannot live for a day under the threat of a single North Korean nuclear weapon capable of reaching major US cities.”

It comes after Mr Trump said the US was ready with a “military option” to end the crisis with North Korea amid the escalating rhetoric between the two countries, saying this would be “devastating for North Korea”.

Speaking at a White House news conference on Tuesday alongside Spain's Prime Minister Mariano Rajoy, he said: “We are totally prepared for the second option, not a preferred option.,

“But if we take that option, it will be devastating, I can tell you that, devastating for North Korea. That's called the military option. If we have to take it, we will.”

The President proceeded to say that North Korean Foreign Minister Ri Yong-ho – who said over the weekend that it was “inevitable” that North Korean rockets would hit the US mainland as part of its expanding nuclear ambitions – was acting “very badly, saying things that should never be said”.

Mr Ri had also claimed Mr Trump had issued a declaration of war in tweeting that North Korean leaders “won't be around much longer” if they keep threatening the US.

Mr Trump and Mr Kim have hurled a series of insults at one another in recent weeks, with the President calling Mr Kim “Rocket Man” and claiming he was on a “suicide mission”.

Mr Kim followed up by calling Mr Trump a “dotard” – a phrase used to describe an elderly, senile person – and a “frightened dog”.