The US leader used his maiden speech at the UN General Assembly to deliver a blistering warning to Pyongyang, after it tested its sixth and largest nuclear bomb and responded to new sanctions by launching its longest-ever missile flight over Japan.
President Trump said Tuesday that North Korean leader Kim Jong-Un was "on a suicide mission for himself and for his regime".
If the US is "forced to defend itself or its allies, we will have no choice but to totally destroy North Korea".
Far from persuading Kim to give up his drive for nuclear weapons, analysts said Trump's speech could have the opposite effect.
"With those words, President Trump handed the Kim regime the soundbite of the century," said Marcus Noland at the Peterson Institute for International Economics.
"It will play on a continuous loop on North Korean national television" as proof that Pyongyang needs an effective deterrent against what it views as American aggression.
Joel Wit, senior fellow at the US-Korea Institute at Johns Hopkins University, said despite the bluster, it was far from clear that Washington was ready to pay the human price for a conflict.
But he added President Trump was a "wildcard and it's hard for anyone to figure out when he is serious and when he isn't".
The US has 28,500 US troops stationed in the South, a legacy of the 1950-53 Korean War which ended in a ceasefire rather than a peace treaty.
Aside from the burgeoning nuclear threat, North Korean artillery bristles on the tense frontier, putting nearby Seoul and its millions of inhabitants in the crosshairs of conventional -- and chemical -- weapons.
Japan and its megacities are also within easy reach of Pyongyang's missiles.
Any US attack would risk massive retaliation with a potentially catastrophic loss of life.
Earlier this year President Trump's former chief adviser Steve Bannon told The American Prospect: "There's no military solution, forget it."
President Trump's comments probably sound to North Korean ears like empty threats, said Wit.
"I suspect they think they are going to prove (Trump) to be a paper tiger," he told AFP.
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