Rudiger Frank, one of the world's leading experts on the secretive rogue state, said North Korean leader Kim Jong Un would have "no choice" but to retaliate if Donald Trump orders a preemptive missile strike on the country.
He said where previous 'rituals" had existed betwen North Korea and the US regarding atomic threats, the arrival of President Trump and North Korea's latest breakthrough meant the situation was now "dangerous".
But he said there was a small chance Washington and Pyongyang could yet back down and begin negotiating.
Mr Frank, who regularly visits North Korea and lectures at several universities in the South, told Stern magazine: "Playing with atomic deterrence is fundamentally risky.
Kim Jong UN and Donald Trump are on the brink of war
"However, so far there has been something like unofficial rules, a kind of ritual – the North Koreans test, and the West protests and sanctions.
"This has worked for many years. Now, however, there is a new president in the US, and North Korea's weapons programme is about to make a breakthrough.
"This changes the situation and makes it more dangerous."
Tensions between North Korea and the US reached a new high when President Trump ordered the USS Carl Vinson aircraft carrier group to head for the Korean peninsula in an attempt to deter North Korea’s suspected nuclear testing.
Pyongyang reponded by warning a thermo-nuclear war could "break out any moment" if the President continued to provoke North Korea.
The USS Carl Vinson is posted off the Korean peninsula before a possible nuclear test by North Korea
Asked how Kim would respond to a premptive strike by the US, Mr Frank said: "Kim Jong Un has no choice but to respond militarily.
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"Otherwise, he is done domestically and the next attack would be pre-programmed anyway. It's unclear whether he would respond to three missiles with three missiles, or immediately order a general attack, assuming that he has only this one attempt.
"In the end, the Korean Peninsula will be a smoking field of rubble with millions of corpses, not to mention the geopolitical consequences."
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Fri, April 14, 2017
North Korea has begun preparing festivities for the 'Day of the Sun,' a holiday celebrating communist leader Kim Il-Sung
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Military officers visit the birthplace of North Korean founder Kim Il Sung, a day before the 105th anniversary of his birth, in Mangyongdae, just outside Pyongyang
The Korean Peninsula will be a smoking field of rubble with millions of corpses, not to mention the geopolitical consequences
German-born Mr Frank said the only way to find a peaceful resolution to the crisis would be for the North Korea nuclear programme to go.
"North Korea wants to be a sovereign and economically successful state, which is not possible without international cooperation or at least toleration," he said.
"Nuclear weapons are ultimately in the way, and the North Koreans know this too.
There is therefore a basic willingness to negotiate – but not to capitulate."