Kim Jong-un has warned he will change course on denuclearisation if the US continues its sanctions.
The North Korean leader, during his closely-watched annual New Year's address, added that he is ready to meet US President Donald Trump at any time.
His comments came after last year's speech set the country on an unprecedented path of international diplomacy with South Korea and the US.
Mr Kim met US President Donald Trump to discuss denuclearisation in June 2018 but with few results so far.
In his latest New Year address, Kim said denuclearisation is his "firm will" and suggested that North Korea would no longer produce nuclear weapons.
But also urged Washington to take unspecified corresponding action to speed up the stalled diplomatic process.
North Korea might be "compelled to explore a new path" to defend its sovereignty if the United States "seeks to force something upon us unilaterally ... and remains unchanged in its sanctions and pressure," Kim said in his nationally televised address.
The comments are likely to fuel growing scepticism over whether Pyongyang intends to give up the nuclear weapons programme that it has long considered essential to its security.
There was no immediate reaction from the US State Department, but South Korea's presidential office welcomed Kim's speech, saying it carried his "firm will" to advance relations with Seoul and Washington.
Kim and Mr Trump vowed to work towards denuclearisation and build "lasting and stable" peace at their landmark summit in Singapore in June, but little progress has been made since.
Pyongyang has demanded Washington lift sanctions and declare an official end to the 1950-53 Korean War in response to its initial, unilateral steps toward denuclearisation, including dismantling its only known nuclear testing site and a key missile engine facility.
Those measures were in line with its resolve to "no longer make, use or spread" nuclear weapons, Kim said, indicating a possible moratorium on weapons production for the first time.
Although Pyongyang did not conduct nuclear or missile tests last year, satellite images have pointed to continued activity at the North's related facilities.
U.S. officials say those initial steps were not confirmed and can be easily reversed, and have called for strict sanctions enforcement on the impoverished country until full, verifiable disarmament.
Washington halted some large-scale military exercises with Seoul to aid nuclear negotiations, but smaller drills continued.
Kim called for South Korea to "completely stop" joint military drills with the United States involving strategic assets, while multilateral negotiations among countries involved in the armistice agreement should be pursued to build a permanent peace regime.
