North Korean leader Kim Jong Un said he will “exponentially increase” nuclear weapon production in 2023 to counter perceived threats from the U.S. and South Korea, according to state media on Sunday.

Speaking on the last day of a six-day party plenary meeting (plenum), Kim said “another new intercontinental ballistic missile (ICBM) system” with “rapid nuclear counterattack ability” is under development, likely referring to a missile using a solid-fuel engine tested in December.