North Korea says because the United States had ignored a year-end deadline for nuclear talks, it no longer felt bound by its commitments, which included a halt to its nuclear testing, and may "seek a new path".
North Korean leader Kim Jong Un set a December 31 deadline for denuclearisation talks with the US and White House national security adviser Robert O'Brien said they had opened channels of communication.
O'Brien said he hoped Kim would follow through on denuclearisation commitments he made at summits with US President Donald Trump.
But Ju Yong Chol, a counsellor at North Korea's mission to the United Nations in Geneva, told the UN-backed Conference on Disarmament: "We found no reason to be unilaterally bound any longer by the commitment that the other party fails to honour."
Speaking as the envoy from the Democratic People's Republic of Korea (DPRK), he accused the US of applying "the most brutal and inhuman sanctions".
"If the United States persists in such hostile policy towards the DPRK there will never be the denuclearisation of the Korean peninsula," he said.
"If the United States tries to enforce unilateral demands and persists in imposing sanctions, North Korea may be compelled to seek a new path," Ju added.
North Korea warned in December that it may take an unspecified "new path" if the United States failed to meet its expectations with a new approach to negotiations.
US military commanders said the move could include the testing of a long-range missile, which North Korea has suspended since 2017, along with nuclear warhead tests.
Pyongyang has rejected unilateral disarmament and given no indication that it is willing to go beyond statements of broad support for the concept of universal denuclearisation.
It has said in previous, failed talks, that it could consider giving up its arsenal if the United States provided security guarantees by removing its troops from South Korea and withdrew its so-called nuclear umbrella of deterrence from South Korea and Japan.
Australian Associated Press