|US military exercises with South Korea are viewed as a provocation by the North|
It views the annual drills, which have now got under way, as a provocation and a practice for invasion.
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The manoeuvres come amid a war of words between North Korean leader Kim Jong Un and US President Donald Trump, who has threatened to unleash "fire and fury" if America and its allies are threatened.
Last month, Pyongyang tested two long-range rockets, which experts said brought major US cities within range .
In turn, Mr Kim has threatened to fire missiles towards the US territory of Guam in the Pacific Ocean.
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It warned the exercises would "be like pouring gasoline on fire and worsen the state of the peninsula" and added: "If the United States is lost in a fantasy that war on the peninsula is at somebody else's doorstep far away from them across the Pacific, it is far more mistaken than ever."
Mr Kim has said North Korea can target the US "anytime and neither Guam, Hawaii nor the mainland can dodge the merciless strike".
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About 17,500 US troops will participate in this year's drills, which represents a reduction from last year.
US defence secretary James Mattis said the smaller troop numbers were "by design to achieve the exercise objectives".
"This right now is an exercise to make certain that we're ready to defend South Korea and our allies over there," he added.
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