North Korea took aim at President Trump on Monday, dubbing him a "heedless and erratic old man," after he tweeted leader Kim Jong Un wouldn't want to "void his special relationship" with him or the U.S. by interfering in the 2020 election by acting "in a hostile way."

The country won't cave to U.S. pressure because it has nothing to lose, Kim Yong Chol, a senior North Korean official and former nuclear negotiator, said in a statement. The North accused Trump of trying to buy time ahead of an end-of-year deadline set by Kim Jong Un for Washington to salvage nuclear talks.

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Trump tweeted Sunday that Kim was "too smart and has far too much to lose, everything actually, if he acts in a hostile way. He signed a strong Denuclearization Agreement with me in Singapore."

"He does not want to void his special relationship with the President of the United States or interfere with the U.S. Presidential Election in November. North Korea, under the leadership of Kim Jong Un, has tremendous economic potential, but it must denuclearize as promised," he added. "NATO, China, Russia, Japan, and the entire world is unified on this issue!"

The Denuclearization Agreement referenced was a vague statement issued by Trump and Kim during their first summit in Singapore in June 2018 that called for a nuclear-free Korean Peninsula without describing when or how it would occur.

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Trump's tweets, according to Kim Yong Chol, show he's an angry old man “bereft of patience.”

“As (Trump) is such a heedless and erratic old man, the time when we cannot but call him a ‘dotard’ again may come,” the North Korean official said. "Trump has too many things that he does not know about (North Korea). We have nothing more to lose. Though the U.S. may take away anything more from us, it can never remove the strong sense of self-respect, might and resentment against the U.S. from us.”

Nuclear negotiations between the North and the U.S. paused after a February meeting between Trump and Kim in Vietnam broke down when the U.S. side rejected North Korean demands for broad sanctions relief in exchange for a partial surrender of its nuclear capabilities.

Kim has said North Korea will seek a “new way” if the U.S. maintains its sanctions and pressure, and issued the deadline for the Trump administration to offer mutually acceptable terms for a deal.

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Trump and Kim met for a third time in June at the border between the two Koreas and agreed to resume talks. But an October working-level meeting in Sweden broke down over what the North Koreans described as the Americans’ “old stance and attitude.”

The Associated Press contributed to this report.