Kim Yo Jong, the powerful sister of North Korea’s leader Kim Jong Un, warned joint military exercises of the US, South Korea, and Japan could bring about “negative consequences” for themselves, state media reported on Sunday.

South Korea, Japan and the US will conduct annual defensive drills called the “Freedom Edge” starting on September 15 to upgrade aerial, naval and cyber operational capabilities against North Korea’s nuclear and missile threats, South Korea’s military has said.

“This reminds us that the reckless display of power displayed by the US, Japan, and South Korea in the wrong places, namely around the Democratic People’s Republic of Korea, will undoubtedly bring about negative consequences for themselves,” Kim said via the state KCNA news agency.

South Korea and the United States also plan to stage the “Iron Mace” tabletop exercises next week on integrating their conventional and nuclear capabilities against North Korea’s threats, South Korean local media reported.

If “hostile forces” continue to boast about their power through those joint drills, North Korea will take countermeasures “more clearly and strongly”, North Korea’s top party official Pak Jong Chon said in a separate dispatch via KCNA.

Pyongyang has traditionally criticised those joint drills as rehearsals for invasion and in some cases responded with weapons tests, but Seoul and Washington say they are purely defensive.