North Korean leader Kim Jong Un hit back at President Trump Thursday, saying the U.S. president would “pay dearly for his speech” before the U.N. General Assembly.

Describing Trump as a “mentally deranged U.S. dotard,” and referring to the U.S. president’s speech as “unprecedented rude nonsense,” Kim reiterated his unwillingness to abandon Pyongyang’s nuclear arsenal. Instead, according to Kim, Trump’s speech, “convinced me” that “the path I chose is correct and that is one that I have to follow to the last.”

In a rare, and long statement, Kim said he was weighing his options before responding with greater action. “I am now thinking hard about what response he could have expected when he allowed such eccentric words to trip off his tongue.”

On Tuesday, Trump vowed to “totally destroy” North Korea if the U.S. was forced to defend itself or its allies against Pyongyang’s burgeoning nuclear threat.

Trump’s fiery speech earned a muted response from other world leaders hoping to quell escalating tensions. That didn’t seem to dissuade the Trump administration from continuing with the threats: Nikki Haley, ambassador to the U.N., said in a press briefing Thursday that the U.S. continues to entertain a variety of “military options.”

In Kim’s long statement to Trump, which was carried by North Korean state media KCNA, the erratic North Korean leader said Trump was “unfit to hold the prerogative of supreme command of a country, and is surely a rogue and a gangster fond of playing with fire, rather than a politician.”

Kim’s comments came hours after President Trump announced a fresh round of sanctions focused on North Korea’s shipping, banking, and “trade networks.”

Flanked by Vice President Mike Pence and Secretary of State Rex Tillerson, Trump said his new executive order would give the Treasury Department greater authority to impose economic sanctions on North Korea and international entities that do business with the pariah state, including Chinese companies known to skirt existing U.N. and U.S. sanctions.

Treasury Secretary Steve Mnuchin said he called the People’s Bank of China earlier in the day to let them know the order was coming, but stressed that these new U.S. sanctions on financial institutions were not specifically directed at China.