"If [Trump] was thinking about surprising us with dog-barking sounds then he is clearly dreaming", Ri told reporters gathered outside his hotel near the United Nations headquarters in NY.
"I certainly don't rule out that this administration could decide that a North Korean nuclear weapon on an ICBM is a big enough threat to overrule the concerns that [crippling sanctions on a big Chinese bank] could harm both economies and crack the trade relationship", he said.
"I will make the man holding the prerogative of the supreme command in the US pay dearly for his speech calling for totally destroying [North Korea]", Kim said.
North Korea is too close to crossing the red line - deploying nuclear missiles that can destroy a USA city - and President Trump must take military action.
The U.S. president said in his first address to the United Nations on Tuesday he would "totally destroy" the country of 26 million people if the North threatened the United States and its allies, and called Kim a "rocket man" on a suicide mission.
Kim said the North would consider the "highest level of hard-line countermeasure in history" against the United States and that Trump's comments had confirmed his own nuclear programme was "the correct path".
China accounts for some 90 per cent of the North's trade, making its cooperation critical to any efforts to derail Pyongyang's development of nuclear weapons and long-range missiles.
Later, North Korea's top diplomat said his country may test a hydrogen bomb in the Pacific Ocean to fulfil leader Kim Jong Un's vow. Along with Russia, China wants the U.S.to seek dialogue with the North.
Ri did not elaborate on when the detonation might take place and added that any final decision on the matter would be taken by North Korean leader Kim Jong Un. At times like this, the South Korean government needs to be all the more clear about its commitment to not allowing war on the peninsula and to solving the North Korean nuclear issue through peaceful means.
It was reminiscent of 2002, when then-President George W. Bush denounced North Korea, Iran, and Iraq as an "axis of evil". Kim described Trump as "a madman" and "a frightened dog" and "a mentally deranged U.S".
China said on Saturday it will ban exports of some petroleum products to North Korea, as well as imports of textiles from the isolated North, in line with a United Nations Security Council resolution passed after Pyongyang's latest nuclear test.
Vipin Narang, an associate professor of political science at Massachusetts Institute of Technology, said he could not recall such a statement in the first person, authored and signed by Kim.
When asked when we'll know for sure if North Korea has a nuclear-tipped missile, nonproliferation expert Jeffrey Lewis sometimes responds with a bleak joke: "you'll see a giant bright light".
The president's bellicose rhetoric was in turn answered by Kim in a rare personal statement broadcast on state television.
The aim of this action would be to keep North Korea from continuing with its nuclear program.