North Korea has lashed out at the US for continuing to push for sanctions enforcement, BBC reports.
Pyongyang said there would be no progress towards denuclearisation if the US followed an "outdated script".
It accused US negotiators of going against the intentions of President Donald Trump and the spirit of the summit in Singapore.
Mr Trump and North Korean leader Kim Jong-un agreed at the June meeting to work towards denuclearisation.
But the details of that process remain vague - North Korea did not commit to unilaterally give up its nuclear weapons and the UN says its nuclear programme is continuing.
The US has insisted it is vital to maintain diplomatic and economic pressure on the North.