The top U.S. official on North Korea policy slammed recent statements from Pyongyang as “provocative” and said Washington will be “prepared” for nuclear and missile tests as North Korea readies celebrations for one of its biggest holidays next week.

The remarks came after North Korean leader Kim Jong Un’s high-ranking sister Kim Yo Jong threatened the “extermination” of South Korean armed forces after Seoul’s defense minister described capabilities to hit North Korean missile launch points.