Ri Yong Ho, who is in the US for the United Nations General Assembly, said he "felt sorry" for the President's advisers after a fiery speech to the UN on Tuesday.
In his debut address to world leaders, Trump vowed to "totally destroy" North Korea if the US was forced to defend its allies.
Referring North Korean leader Kim Jong Un by a nickname he first used in in a tweet Sunday
, Trump said: "Rocket man is on a suicide mission for himself and for his regime."
Ri, in his country's first response to Trump's speech, was derisive. "If he was thinking he could scare us with the sound of a dog barking, that's really a dog dream," Ri told reporters outside his hotel in New York. In Korean, a dog dream is one that is absurd and makes little sense.
When asked about Trump's use of the "rocket man" nickname, Ri said: "I feel sorry for his aides."
Though Trump's speeches typically employ colorful rhetoric, threatening another country with destruction was unprecedented for a US President and took diplomats aback.
North Korean diplomats were not present for Trump's speech.
Little chance of meeting
US Secretary of State Rex Tillerson is also in New York, but played down the possibility of a meeting with his North Korean counterpart.
Pyongyang and Washington do not maintain formal diplomatic relations and the presence of North Korea's top diplomat in the US could have afforded a rare chance for high-level, face-to-face dialogue.
Tillerson told reporters he did not believe he could have a "matter-of-fact discussion with North Korea because we don't know how their means of communication and behavior will be."
Tillerson claimed there were signs that increased international pressure on North Korea was starting to bear fruit. He said there was evidence of fuel shortages in the country after the passage of recent UN sanctions
, which targeted oil imports among other things.
However, analysts pointed out that fuel shortages did not necessarily prove that sanctions were having an effect, as most North Koreans don't own cars or use fuel at anywhere near the rate of the rest of the world.
Anthony Ruggiero, an expert in the use of targeted financial measures at the Foundation for the Defense of Democracies, said sanctions rarely hit fast. Any lines for gas were "probably more due to the regime stockpiling fuel in anticipation that China would implement the restriction," Ruggiero, who worked at both the State Department and Treasury Department, told CNN.
Trump is scheduled to meet with Japanese Prime Minister Shinzo Abe and South Korean President Moon Jae-in Thursday, two important US allies on North Korea's doorstop.
Top of the agenda is likely to be South Korea's surprise decision to send an $8 million aid package to North Korea. The move, which runs contrary to the US and Japan's calls for an increase in economic and diplomatic pressure, marks a resumption in South Korean aid after a break of almost two years.
In statement Wednesday, the South's Unification Ministry said the decision to resume aid was in line with "the government's stance that it separates the provision of humanitarian aid from politics and it continues to provide aid to improve the humanitarian situation of North Korean residents and the quality of their lives."
The South said it planned to send $4.5 million worth of medical treatments, nursery facilities and nutritional products for children and pregnant women through the World Food Programme, and $3.5 million worth of medicinal treatments and nutritional products through UNICEF.
The precise timing and actual provision would be dependent on various factors, including "inter-Korean relations," the ministry said in a statement.
Trump spoke with Chinese President Xi Jinping about the North Korean situation in a phone call Monday, the White House said. Accounting for about 90% of North Korea's imports, Beijing is seen by many as the key to any North Korea strategy.
While China voted in favor of the two most recent UN resolutions against North Korea, Chinese diplomats have called for calm as Trump's rhetoric has heated up, and editorials in Chinese state media have continued to assail the US President's approach to diplomacy.
"It is time for the US to realize that irresponsible words and actions are backing the DPRK into a corner with no way out, and it would be a tragedy if Trump's risky game of chicken with the DPRK crosses the point of no return," read an editorial published Thursday in the People's Daily
, the official newspaper of the Chinese Communist Party.
"Rather than hurl threats and try to pass the buck to China, the US should accept its responsibility, and do more to resolve the issue through dialogue and negotiation."