A sticking point in talks has been how to verify North Korea's disarmament
The US has accused Pyongyang of violating a six-nation nuclear accord and said North Korea would remain on the State Sponsors of Terrorism list.
Earlier, Pyongyang said it had stopped disabling its nuclear facilities, and accused the US of reneging on a deal to take it off a list of terror sponsors.
Work was suspended on 14 August, a foreign ministry spokesman said.
Washington said it wants to agree more stringent verification processes before it takes North Korea off the blacklist.
"The United States will not take North Korea off the State Sponsors of Terrorism list until we have a protocol in place to verify the dismantling and accounting for Korea's nuclear programme," said White House spokesman Tony Fratto.
He added that increasingly strained tensions between Russia and the US over Moscow's military push in Georgia had not affected their collective efforts to convince North Korea to give up its nuclear weapons program.
"I'm not aware of any degradation of our cooperation with respect to the six-party talks," said Mr Fratto.
"It is not in Russia's interest to have a nuclear armed nation on its border."
North Korea finally submitted a long-delayed account of its nuclear facilities to the six-party talks in June - and was expecting to be removed from the US list of terrorism sponsors in return.
But that move was delayed amid wrangling among the six parties - North and South Korea, the US, China, Russia and Japan - over how to verify the North's declaration.
In its latest move, Pyongyang has also threatened to restore facilities at its main Yongbyon plant - where the main cooling tower was spectacularly demolished in late June in a symbol of Pyongyang's commitment to disarmament.
The submission by North Korea of a nuclear dossier was seen by the Bush administration as one of its success stories in foreign policy, says the BBC's diplomatic correspondent Jonathan Marcus.
The question now is whether this latest spat is just another hiccup in relations or represents a serious blow to progress.
With only months to go until a new team takes office in Washington, Pyongyang may be looking to the next administration for a better deal, our correspondent says.
"As the US side failed to keep its own side of the agreement, we cannot but take the following measures under the principle of action for action," a North Korean foreign ministry spokesman told the state news agency KCNA, according to AFP news agency.
"First, we've decided to stop the denuclearisation process that has been under way in accordance with the 3 October agreement. This measure already took effect on 14 August and relevant parties have already [been] informed," the official said.
"Second, we will consider restoring the Yongbyon facilities to their original state in accordance with strong demands from our relevant agencies."
Analysts say that, in addition to the delay removing it from the US terrorism list, the North has been angered by recent military drills jointly undertaken by US and South Korean forces.