We are a long way from hamburgers. In a bout of blistering invective rare even for cantankerous North Korea, Supreme Leader Kim Jong Un has taken personal aim at Donald Trump, vowing to “surely and definitely tame the mentally deranged U.S. dotard with fire,” in response to the U.S. President’s threat during his inaugural speech at the U.N. General Assembly on Tuesday to “totally destroy” the Hermit Kingdom if it did not halt its weapons program. (A “dotard” is a mentally frail old person.)

Kim’s tirade came just as Trump signed a new executive order ramping up sanctions against the secretive regime, authorizing the U.S. Treasury to target firms and financial institutions conducting business there. It also spotlights sharply deteriorating relations with the Stalinist state in stark contrast to Trump’s offer during his campaign to meet the 33-year-old Kim “for a hamburger” and to cut “a good deal” over halting his weapons program.

But confronted with Pyongyang’s escalating missile and nuclear tests — it has tested 22 missiles and its sixth nuclear bomb this year alone — Trump has resorted to the Obama administration’s tactics of attempting to isolate the regime through U.N. sanctions. The former reality TV star has, however, added some trademark bluster, personally mocking Kim as “Rocketman” both on Twitter and before world leaders at the U.N. “Rocketman is on a suicide mission,” Trump told the General Assembly.

The disrespectful tenor has clearly irked the young despot, who replied with a 500-word diatribe on state media KCNA. Analysts say the unprecedentedly fiery exchanges makes a devastating miscalculation much more likely.

“[Trump] is unfit to hold the prerogative of supreme command of a country, and he is surely a rogue and a gangster fond of playing with fire, rather than a politician,” said Kim. “Far from making any remarks of any persuasive power that can be viewed to be helpful in diffusion tension, he made unprecedented rude nonsense no one has ever heard from any of his predecessors.”

That is certainly true, and Kim has made the most of the opportunity to ratchet up provocations in turn, firing two missiles over Japan in the last month, where missile alert drills are now part of local preparedness training. North Korea’s last missile, on Sept. 15, flew 2,300 mi., so 200 mi. further than the U.S. Pacific territory of Guam, which is 2,100 mi. from Pyongyang.

“Trump’s ‘totally destroy’ statement is such an extraordinary gift to North Korea,” says Daniel Pinkston, an East Asia expert at Troy University in South Korea. “They will just use this stuff to justify what they are doing both internally and externally.”

According to North Korean Foreign Minister Ri Yong Ho, that might include a hydrogen bomb test in the Pacific Ocean, similar to 120-kiloton device the regime detonated underground Sept. 3.

“It could be the most powerful detonation of an H-bomb in the Pacific,” said Ri, according to South Korean news agency Yonhap. “We have no idea about what actions could be taken as it will be ordered by leader Kim Jong Un.”

Attempting to defuse tensions was South Korean President Moon Jae-in, who on Thursday gave a measured speech at the General Assembly, saying, “We do not desire the collapse of North Korea.”

“We will not seek reunification by absorption or artificial means,” Moon added. “If North Korea makes a decision even now to stand on the right side of history, we are ready to assist North Korea together with the international community.”

On Thursday, Moon’s government approved an $8 million humanitarian aid package to North Korea, mostly medical supplies for pregnant women and children. It’s the first South Korean aid heading north for almost two years, though stands to upset Washington’s attempts to isolate the regime.

Moon, the son of refugees from the North, was elected to the Blue House on promises to restart measured engagement with the Kim regime, though Pyongyang’s escalating tests have seen those efforts stillborn. Moon is walking an ever-fraying tightrope between appearing supportive of Trump while trying to dial back his most volcanic utterances. Moon’s office even issued a statement in support of Trump’s “totally destroy” threat, despite prevailing opinion being highly critical.

“Moon is doing what he needs to do,” says Pinkston. “Heads of state realize that establishing and maintaining close personal relationships with Trump is beneficial to their bilateral relationships. Trump has this desire to be praised.”

Trump also said Thursday that Beijing has agreed that China’s central bank would instruct all Chinese banks not to do business with North Korea. There was no official confirmation from China at time of publishing, though Reuters cites multiple sources corroborating its veracity.

If confirmed, it would be a major step in cutting off the foreign cash the Kim regime channels toward its weapons program. North Korea’s economy grew 3.9% last year, according to South Korea’s central bank, as its chiefly agrarian population of 25 million enjoyed an improved harvest after El Nino-ravaged 2015. But the regime’s nuclear ambitions are dependent on foreign cash earned through licit and illicit businesses, largely involving China, where smuggling networks ply the 880-mile shared frontier. Already, imports of coal have been halted and restrictions put on North Korean workers abroad. But other revenue streams remain open and lucrative, such as cybercrime and peddling drugs and weapons.

“A lot of revenue comes from selling small arms to militant groups in sub-Saharan Africa and the Middle East who are themselves under sanctions,” Anwita Basu, an analyst specializing in North Korean economy for the Economist Intelligence Unit, tells TIME. “There are plenty of rogue states out there.”

Even were these revenue streams cut off, some analysts say that the regime has enough cash squirreled away to reach its end goal of a nuclear-armed ballistic missile capable of striking the continental U.S. And while Beijing and Moscow both say negotiations are the best route forward, Trump’s insults seem to have stiffened Kim’s resolve.

“[Trump’s remarks] have 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,” he wrote.

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