The US and South Korea said Sunday they would delay annual joint aerial exercises slated for this month in an act of "goodwill" after months of deadlocked nuclear talks.

Pyongyang has long protested the joint drills, which it condemns as preparations for invasion, and Seoul and Washington last year cancelled several training sessions in the wake of the Singapore summit between President Donald Trump and the North's leader Kim Jong Un.

But Kim Yong Chol, a senior North Korean official who formerly led talks with the US, said the weekend postponement was irrelevant.

"We demand that the US quit the drill or stop it once and for all," Kim said in a statement carried by the KCNA news agency.

"The suspension of the drill does not mean ensuring peace and security on the Korean peninsula and is not helpful to the diplomatic efforts," he added.

The North had "no intention" to sit down with the "tricky US" and would not return to talks "before the complete and irrevocable withdrawal of its hostile policy".

"From now on, the DPRK will get due compensation for every administrative achievement the US president has talked too much about for over a year," Kim added, referring to the North by its official name.

Trump has repeatedly pointed to North Korea's moratorium on nuclear tests and intercontinental ballistic missile launches as foreign policy successes for him.

But negotiations have been gridlocked since the Hanoi summit in February broke up in disagreement over sanctions relief, while October's working-level talks rapidly broke down in Sweden.

Pyongyang also criticised Stockholm on Tuesday, saying it had passed on a US suggestion of meeting again in December.

The US used the intermediary "not to give impression that it fawns on the DPRK", the North's chief nuclear negotiator Kim Myong Gil told KCNA.

But now that Pyongyang and Washington know each other's position, Stockholm "no longer needs to work for the DPRK-US dialogue", he said.

"If the Swedish side behaves like a back-seat driver, it might be regarded as unreasonable," he added. "The Swedish side would be well-advised to properly understand the situation and behave itself."

Tuesday's statements were the latest in a series of increasingly assertive comments from the North as its end-of-year deadline for the US to come up with a fresh offer approaches, and it has also carried out multiple weapons tests in recent weeks.

Trump hinted at the prospect of a fourth meeting with Kim in a tweet at the weekend, only to be dismissed by the North, which said it had no interest in summits "that bring nothing to us".