South Korea and the United States will face even greater security threats for going ahead with scheduled joint military drills due to begin this week, Kim Yo Jong, a powerful North Korean official and sister of leader Kim Jong Un said Tuesday.

South Korea and the United States will begin preliminary military drills on Tuesday, the Yonhap news agency reported on Monday, despite nuclear-armed North Korea's warning that the exercises would set back progress in improving inter-Korean relations.

The drills are an "unwelcome, self-destructive action" that threaten the North Korean people and raise tensions on the Korean Peninsula, Kim Yo Jong said in a statement carried by the state-run Korean Central News Agency.