North Korea accused US President Joe Biden of pursuing a hostile policy, dismissing "spurious" American diplomacy and warning of a response.
Mr Biden on Wednesday said his administration would deal with the threat posed by Pyongyang's nuclear programme "through diplomacy as well as stern deterrence".
The White House said on Friday that the president was open to negotiations with North Korea on denuclearisation following the completion of a policy review, but on Sunday Pyongyang said Mr Biden made a "big blunder".
"His statement clearly reflects his intent to keep enforcing the hostile policy towards the DPRK as it had been done by the US for over half a century," Kwon Jong Gun, a Foreign Ministry official, said in comments reported by the state KCNA news agency.
"The US-claimed 'diplomacy' is a spurious signboard for covering up its hostile acts, and 'deterrence' touted by it is just a means for posing nuclear threats to the DPRK," Mr Kwon said, using the official name of North Korea.
"Now that what the keynote of the US new DPRK policy has become clear, we will be compelled to press for corresponding measures."
The White House said its goal remained "the complete de-nuclearisation of the Korean peninsula".
Mr Biden's press secretary, Jen Psaki, gave little indication of what kind of diplomatic initiative this could entail, but suggested that Mr Biden learnt from the experience of his predecessors, who struggled to deal with North Korea's leadership and its nuclear weapons programme.
But Ms Psaki said Washington would not "focus on achieving a grand bargain", apparently referring to the kind of dramatic overarching deal that former president Donald Trump initially suggested was possible when he met with North Korea's leader, Kim Jong-un.
Neither would the White House follow the more stand-offish approach espoused by Barack Obama, she said.
In a separate statement through KCNA on Sunday, North Korea also accused the US of insulting its leadership and its anti-coronavirus measures, referring to a State Department press release on April 28.
Human rights row
US State Department spokesman Ned Price issued a statement that day criticising North Korea's human rights abuses and draconian Covid-19 curbs, describing it as "one of the most repressive and totalitarian states in the world".
"The 'human rights issue' touted by the US is a political trick designed to destroy the ideology and social system in the DPRK," the North Korean Foreign Ministry said.
In a third statement issued on Sunday, Kim Jong-un's sister, Kim Yo-jong, criticised South Korea over a recent anti-Pyongyang leaflet campaign by a defector group.
Activist groups have long sent flyers critical of the North Korean leadership across the Demilitarised Zone dividing the peninsula, either flying them in by hot air balloon or floating them across rivers.
The leaflets have infuriated Pyongyang, which issued a series of vitriolic condemnations last year demanding Seoul take action. Pyongyang upped the pressure by blowing up an inter-Korean liaison office on its side of the border.
South Korean MPs rapidly passed a law criminalising the leaflet campaigns in December, raising concerns over freedom of speech.
But a defector group said it flew 500,000 leaflets near the DMZ last week in defiance of the law.
Kim Yo-jong blamed the South Korean authorities for not stopping them.
"We regard the manoeuvres committed by the human wastes in the south as a serious provocation against our state and will look into corresponding action," she said.