Pyongyang's deputy UN ambassador, Ri Tong Il, also repeated that his government "made it very clear we will carry out a new form of nuclear test" but refused to elaborate, saying only that "I recommend you to wait and see what it is."
His comments came at North Korea's second press conference at the United Nations in two weeks.
Ri blamed the US for aggravating tensions on the Korean Peninsula by continuing "very dangerous" military drills with South Korea, by pursuing action in the UN Security Council against his country's recent ballistic missile launches and by going after Pyongyang's human rights performance.
Ri also accused the US of blocking a resumption of six-party talks on its nuclear program by settling preconditions and said Washington's primary goal is to maintain tensions and prevent the denuclearisation of the Korean Peninsula.
A US diplomat who was not authorised to comment publicly later told AP: "We have long made clear - in close consultation with our allies - that we are open to improved relations with the DPRK if it is willing to take clear actions to live up to its international obligations and commitments."
North Korea walked away from the six-party nuclear disarmament talks in 2009 over disagreements on how to verify steps the North was meant to take to end its nuclear programs. The US and its allies are demanding that the North demonstrate its sincerity in ending a drive to acquire nuclear weapons.
Since pulling out of the six-party talks, the North has conducted two nuclear tests, at least two long-range rocket tests and most recently short-range rocket launches.