North Korea has slammed Pentagon chief Lloyd Austin for pledging that the U.S. will continue to deploy strategic assets to the peninsula during his visit to Seoul this week, warning that it will respond to nuclear threats using its weapons of mass destruction.

The Ministry of Foreign Affairs (MFA) released the statement early Thursday, just hours after South Korea’s defense ministry announced that Seoul had conducted a joint air drill involving U.S. bombers on Wednesday, though the statement makes no mention of the exercise.