North Korea says a plan that could see it fire four missiles near the US territory of Guam will be ready in a matter of days.
State media said Hwasong-12 rockets would pass over Japan and land in the sea about 30km (17 miles) from Guam, if the plan was approved by Kim Jong-un.
It denounced Donald Trump’s warnings of “fire and fury” and said the US leader was “bereft of reason”.
The US has warned the North its actions could mean the “end of its regime”.
US Defence Secretary Jim Mattis said Pyongyang would be “grossly overmatched” in any war against the US and its allies.
The BBC’s Rupert Wingfield-Hayes, who is in Guam, says there is a sense that the North Korean threat is rhetorical, as most people feel that if they really did strike with missiles it would be suicidal for the North Korean regime.
What is the North planning?
The North first announced on Wednesday that it had been drawing up plans for a missile strike against Guam, a Pacific island which is home to US military bases, strategic bombers and about 163,000 people.
A later statement carried by state media said the military would “finally complete the plan” by mid-August and send it to leader Kim Jong-un for his approval.