North Korea has cancelled Wednesday's high-level talks with South Korea because of anger over its joint military exercises with the US.
The North's official KCNA news agency said the exercises were a "provocation" and a rehearsal for an invasion.
It also warned the US over the fate of the historic summit between Kim Jong-un and US President Donald Trump that is scheduled for 12 June in Singapore.
In March, Mr Trump stunned the world by accepting an invitation to meet Mr Kim.
"We will both try to make it a very special moment for World Peace!" the US leader later tweeted.
The US state department said it was continuing to prepare for the Trump-Kim summit and that it was not aware of any changes in the North Korean position.
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What exactly has North Korea cancelled?
In short, the scheduled talks with South Korea were a follow-up to a rare summit that was held on 27 April.
They were agreed earlier this week and were set to take place at Panmunjom, a military compound in the demilitarised zone between the two countries that is often referred to as the "truce town".
Representatives had planned to discuss further details of the agreements they had made at the historic summit.
This covers things like ridding the peninsula of nuclear weapons and turning the armistice that ended the Korean War in 1953 into a peace treaty.
Other points the leaders agreed in a joint statement were:
An end to "hostile activities" between the two nations
Changing the demilitarised zone (DMZ) that divides the country into a "peace zone" by ceasing propaganda broadcasts
An arms reduction in the region pending the easing of military tension
Why is it so unhappy?
Joint military drills between the US and South Korea have often angered the North.
In the past, they have threatened an "all-out offensive" in response to the exercises and condemned them as pouring "gasoline on fire".
The latest drills - known as Max Thunder - involve some 100 warplanes, including an unspecified number of B-52 bombers and F-15K jets.
The North has described them as a "provocation" and preparation for a future invasion, which is something they have said before.
But the US and South Korea have always insisted the drills are purely for defence purposes, and based out of a mutual defence agreement they signed in 1953.
They also say the exercises are necessary to strengthen their readiness in case of an external attack.
So what's happening with the Trump-Kim talks?
It depends who you ask.
North Korea fired a warning shot at the US when it announced it was cancelling Wednesday's talks with the South.
"The United States will also have to undertake careful deliberations about the fate of the planned North Korea-US summit in light of this provocative military ruckus jointly conducted with the South Korean authorities," the KCNA report said.
The BBC's South Korea correspondent Laura Bicker says the wording of the statement showed North Korea was casting doubt over talks, rather than saying they were about to be cancelled.
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But the US was quick to resist any suggestion that the summit was now in doubt.
"We will continue to plan the meeting," a state department spokeswoman told reporters soon after the news of the cancelled talks broke.
She added that the US had received "no notification" of a change in the North's position.