– North Korea has long cultivated an image of defiant belligerence, punctuating its propaganda and diplomacy with threats, insults and bluster. But by addressing President Donald Trump in a personal statement Friday, the nation’s leader, Kim Jong Un, has pushed his government’s brinkmanship to a new, potentially more perilous level.

In a statement written in the first person, published on the front pages of state newspapers and read on national television, Kim called Trump a “mentally deranged U.S. dotard” who had “denied the existence of and insulted me and my country in front of the eyes of the world.”

Kim vowed to take the “highest level of hard-line countermeasure in history.”

In a country where the leader is essentially portrayed as a god, Kim’s decision to respond personally to Trump’s speech to the United Nations and pledge reprisals escalated the standoff over the North’s nuclear program in a way that neither he nor his predecessors had done before.

Though the statement made no mention of nuclear weapons, Kim’s intervention appeared to reduce the possibility that his government might retreat or compromise, even in the face of war.

Kim condemned Trump’s threat to “totally destroy” North Korea if the United States is forced to defend itself, and he declared that it had “convinced me, rather than frightening or stopping me, that the path I chose is correct and that it is the one I have to follow to the last.”

Shortly after Kim’s statement was released, his foreign minister, Ri Yong Ho, delivered prepared remarks to reporters outside his hotel in New York, saying that North Korea might conduct the “biggest ever hydrogen bomb test in the Pacific.”

Ri could not have made such an alarming comment without Kim’s approval, although some analysts question whether North Korea has the technology or daring to conduct an atmospheric nuclear test.

Trump responded Friday by further personalizing the dispute. On Twitter, he called Kim “obviously a madman.”

North Korea has often issued statements in the names of its government and its People’s Army, and since taking power in late 2011, Kim has delivered an annual New Year’s Day speech. But Friday’s statement was the first by Kim directed openly at a foreign head of state. Kim’s father and grandfather, who ruled North Korea before him, never made such a statement.

In effect, Kim, whose cultlike leadership rests upon his perceived daring toward North Korea’s external enemies, has turned the nation’s standoff with the U.S. into a personal duel with Trump, analysts said.

“This is totally unprecedented,” said Paik Hak-soon, a longtime North Korea analyst at the Sejong Institute, a think tank outside Seoul. “The way North Korea’s supreme leadership works, Kim Jong Un has to respond more assertively as its enemy gets more confrontational, like Trump has.”

“There is no backing down in the North Korean rule book,” Paik said. “It’s the very core of their leadership identity and motive.”

Analysts said that by putting his reputation on the line with his statement, Kim was now far more unlikely to stand down. Instead, his government was likely to conduct more nuclear and missile tests, they said.

“Trump shot himself in the foot with his unabashedly undiplomatic United Nations General Assembly speech,” said Lee Sung-yoon, a Korea expert at the Fletcher School of Law and Diplomacy at Tufts University. “By threatening to totally destroy North Korea, he created the impression around the world that it is actually the United States — instead of North Korea — that’s motivated by aggression. In effect, Trump gave Kim Jong Un a freebie for another major provocation. Kim will oblige, and claim that it was in ‘self-defense’ against Trump’s unnerving threats.”

North Korea has conducted all of its six nuclear tests deep underground and has stepped up the pace of its missile tests. Some analysts fear that the next step might be for North Korea to try to prove that it can deliver a nuclear warhead on a long-range missile.

It has been 37 years since any nation tested a nuclear weapon in the planet’s atmosphere, reflecting the nearly universal opposition to such tests over fears of the effects of radioactive fallout on human health and the environment. The last one was in 1980, when China fired what was believed to be a nuclear-tipped ballistic missile into a desert more than 1,300 miles from Beijing.