North Korea has said it will not attend a working meeting ahead of the next round of six-party talks on its controversial nuclear programme.
The nuclear dispute has been raging for 22 months
A spokesman told state news agency KCNA that the US was "not interested in making the dialogue fruitful".
He said Pyongyang had been stunned and disappointed by Washington's view that there could be no reward for North Korea freezing its nuclear programme.
The working group was due to meet later this month in New York.
It was to have discussed the next round of six-nation talks - which include South Korea, China, Japan and Russia as well as the US and North Korea.
Those talks are expected to take place by the end of September.
"It is clear that there would be nothing to expect, even
if the DPRK (North Korea) sits at the negotiating table with the US
under the present situation," an unnamed North Korean spokesman told KCNA on Monday.
"The US has destroyed... the foundation for the talks, making it impossible for the DPRK to go to the forthcoming meeting of the working group."
The statement described Washington's stand as "unreasonable", and insisted that the US was reserving the right to use force to disarm North Korea.
"A nuclear freeze is possible... only when the situation
develops in the direction of the US dropping hostile acts
against the DPRK. On the contrary, these acts are escalating," the North Korean statement said.
At the latest six-party talks in June, North Korea offered to freeze
its nuclear programme in exchange for fuel aid and talks on lifting US sanctions.
It said the freeze would be a step towards the eventual dismantling of the programme.
But the US wants the North to go further, and disclose all its
nuclear activities and allow outside monitors into the country.
The nuclear dispute flared up in 2002, when US officials accused North Korea of running a secret nuclear programme in violation of international agreements.
Since then there have been a series of talks in an effort to resolve the crisis, but a deal has yet to be reached.
A senior South Korean official told Reuters news agency that he expected the working group talks and the main six-party talks to go ahead as planned, despite Pyongyang's statement.
"This is the North Koreans putting on pressure," he said.
"I wouldn't want to say that this thing is about
really quitting the six-party process or the working-group
Meanwhile, South Korea's intelligence agency warned on Sunday that Pyongyang might launch a terrorist strike in revenge for the recent airlift of more than 400 North Korean defectors, who had fled to Vietnam, into the South.
The National Intelligence Service said there were no specific signs of a threat, but the warning had been issued for preventative purposes, according to the South Korean newspaper Choson Ilbo.