North Korean Foreign Minister Ri Yong Ho has called US President Donald Trump's address to the United Nations "the sound of a dog barking", brushing aside Trump's remarks that the United States may be forced to "totally destroy" North Korea.

"There is a saying that goes: 'Even when dogs bark, the parade goes on'," said Ri in televised remarks to reporters in front of a hotel near the United Nations headquarters in New York.

"If (Trump) was thinking about surprising us with dog-barking sounds then he is clearly dreaming."

When asked by reporters what he thought of Trump calling North Korean leader Kim Jong Un "rocket man", Ri quipped, "I feel sorry for his aides."

Ri is slated to make a UN speech on Friday.

His comments are the first official reaction from North Korea after Trump had issued his sternest warning yet to Pyongyang in his address to the United Nations, urging member states to work together to isolate the Kim regime until it halts its hostile behaviour.

If North Korea threatens the United States or its allies, Trump said: "We will have no choice but to totally destroy North Korea."

"Rocket man is on a suicide mission for himself and his regime," he added.

South Korea's presidential office had later said Trump's warning to North Korea had been "firm and specific".