North Korea on Friday accused the US of being "hell-bent on regime change" and warned that any manoeuvres with that intention will be viewed as a "red line" that will result in countermeasures.

Pyongyang's deputy United Nations 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: "I recommend you to wait and see what it is."

His comments came at North Korea's second press conference at the UN in two weeks, a surprising rate for the reclusive Communist regime.

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 programme by settling preconditions and said Washington's primary goal is to maintain tensions and prevent denuclearisation of the Korean peninsula.

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 its drive to acquire nuclear weapons.

Since pulling out of the six-party talks, the North has conducted a long-range rocket test, its second-ever nuclear test, and most recently short-range rockets launches.

Using the initials of the Democratic People's Republic of Korea (DPRK), the country's official name, Ri said: "The DPRK has been making strenuous, hard efforts, very generous, toward easing the tensions on the Korean peninsula, but ignoring all this generous position of the DPRK and its proposals, the US went ahead with opening the joint military drills, very aggressive nature, and they're now expanding in a crazy manner the scale of this exercise."

He also rejected as "illegal" a security council statement last week that condemned North Korea's test-firing of two medium-range ballistic missiles as violations of council resolutions.

The deputy ambassador did not answer questions on the detained American Kenneth Bae or on his country's drone programme, which it has been promoting recently.

South Korean experts this week claimed that two small, camera-equipped drones had been flown across the border by the North, calling them crude and decidedly low-tech. Both drones crashed in South Korea.