North Korea intends to develop the capabilities to strike back in the event of a threat to its security as South Korea implements its nuclear submarine program, First Deputy Foreign Minister Jang Kum-chol said. The diplomat called South Korean nuclear submarine program "a serious challenge" to the security and maritime sovereignty of North Korea, and Pyongyang can't just sit by and watch. According to him, South Korea is also negotiating with Washington on issues related to this program. He said that the appearance of nuclear submarines with Seoul could cause "a nuclear domino" effect in the Asia-Pacific region. "The South Korean program for the development of a nuclear submarine will further increase instability on the Korean peninsula," Jang Kum-chol said.