North Korea has warned the United States and South Korea that planned military drills this month will be met with “unprecedentedly persistent and strong counteractions.”

The hermit nation’s Ministry of Foreign Affairs made the threat Friday after South Korea and the U.S. announced joint military drills have been planned that will focus on addressing North Korea’s growing nuclear viability.

“In case the U.S. and South Korea carry into practice their already announced plan for military drills that [North Korea] – with just apprehension and reason – regards as preparations for an aggression war, they will face unprecedentedly persistent and strong counteractions,” the ministry wrote.

North Korea has long accused the U.S. and South Korea of using joint military drills as a pretext for rehearsing an invasion of the isolated communist country.

“This predicts that the situation in the Korean Peninsula and the region will be again plunged into the grave vortex of escalating tension,” the North Korean statement continued.

South Korea called North Korea “our enemy” for the first time in six years in its biennial defense document published on Thursday.”North Korea doesn’t give up its nukes and is persistently posing military threats to us, so the North Korean government and military… is our enemy,” the document read.The country’s description of its rival in defense papers typically reflects the relationship between the two. During past times of animosity, South Korea has referred to its neighbor as the “main enemy,” “present enemy” or “enemy.”