Foreign Minister Ri Yong Ho, who is expected to deliver a keynote address to the assembly on Friday, likened Trump's United Nations speech to the "sound of dogs barking," Yonhap reported.
Ri initially stayed tight-lipped after landing at John F. Kennedy International Airport, refusing to speak to Yonhap reporters who followed the North Korean diplomat soon after his arrival.
Several policemen were dispatched to the terminal, and security agents quickly escorted Ri out of the building.
Yonhap reported a "dour" Ri ignored reporters' questions when he was asked what he thought of Trump's U.N. speech.
In the course of the speech, Trump said if the United States is "forced to defend itself and its allies, we will have no choice but to totally destroy North Korea."
But later after arriving at his hotel outside U.N. headquarters, Ri said Trump's speech did not surprise members of the Kim Jong Un regime.
"There is a saying a procession marches on, even if dogs bark," Ri said. "To think to scare us with the sound of dogs barking, that would truly be a dog dream."
Ri was using a North Korean phrase used to denote nonsense.
The North Korean foreign minister also said he "felt sorry" for Trump's aides, when asked of his opinion of Trump's "Rocket Man" reference.
"No nation on Earth has an interest in seeing this band of criminals arm itself with nuclear weapons and missiles," Trump had said.
"Rocket Man is on a suicide mission for himself and for his regime," he had added, referring to Kim Jong Un.
Ri is expected to defend Kim's nuclear weapons program at the United Nations on Friday.