North Korean leader Kim Jong Un has ordered the development of new intercontinental ballistic missiles and massive production of tactical nuclear weapons to counter threats from the United States and South Korea, state media said on Sunday.

At a key meeting of the ruling Workers’ Party, Kim highlighted the need to boost the country’s nuclear arsenal and secure “overwhelming military power” to defend its sovereignty and security.

Kim accused Washington and Seoul of carrying out a “plot to isolate and stifle” Pyongyang, calling it “unparalleled in human history.”

“He presented the task of developing another intercontinental ballistic missile system with a rapid nuclear counterattack capability as its basic mission,” the official KCNA news agency said.

The report came hours after North Korea fired a short-range ballistic missile off its east coast, in a rare late-night, New Year’s Day weapons test.