"Trump has too many things that he does not know about the DPRK," Kim said, referring to the North's official name, the Democratic People's Republic of Korea. "We have nothing more to lose."

Trump issued the warning in a tweet on Sunday after North Korea announced it conducted a "very important" test at its satellite launch site over the weekend, deepening concerns Pyongyang could restart testing of an intercontinental ballistic missile.

The tweet came a day after Trump warned the North not to interfere with next year's U.S. presidential election, saying he would be "surprised" if the North acted in a hostile way.

The North's official said that the country has no willingness to reconsider what they "should do in the future" because of what Trump said.

"As he is such a heedless and erratic old man, the time when we cannot but call him a 'dotard' again may come," he said.

"Dotard" is an expression North Korea used to ridicule Trump when the two sides exchanged threats and insults in 2017, with Trump belittling the North's leader Kim Jong-un as "little rocket man."

Still, the official said the North Korean leader has not yet used any harsh words against Trump, in an apparent effort to prevent the situation going to the worst.

"But if thing continues to go this way, our Chairman's understanding of Trump may change," the former nuclear negotiator said.

Kim Yong-chol also hinted at a possible military provocation by the North in the near future, saying that they would be "irritated" if Trump "does not get astonished" by the North's action intended "for his surprise."

"If the U.S. has no will and wisdom, it cannot but watch with anxiety the reality in which the threat to its security increases with the passage of time," Kim Yong-chol said.

Trump and Kim Jong-un held their first summit in Singapore in June 2018 and agreed to work toward complete denuclearization of the Korean Peninsula in exchange for U.S. security guarantees.

But little progress has been made since their second summit in Hanoi ended without a deal in February.

The two sides held their last working-level talks in Stockholm in October, but the meeting also broke down with Pyongyang accusing Washington of failing to come up with a new proposal.

Last week, Trump hinted that the U.S. will use military force against North Korea if necessary. The North responded angrily, saying it will take "prompt corresponding actions at any level" if the U.S. uses force against it. (Yonhap)