North Korean leader Kim Jong Un’s sister, Kim Yo Jong, warned the U.S. that Pyongyang will further build up its military and nuclear weapons in response to joint U.S.-South Korea military drills expected to go ahead this month.

“We are spurred to further strengthen our national defense and strong preemptive strike abilities to swiftly respond to any military action that is aimed at us and ... the ever-increasingly hateful U.S. military threats,” Kim said in a statement released by the Korean Central News Agency (KCNA) on Tuesday morning.