He warned that Seoul's nuclear cooperation with Washington on nuclear submarine development will further destabilise the Korean Peninsula and pose a grave challenge to North Korea's security and maritime sovereignty, Yonhap News Agency reported. South Korea unveiled a program in May, called the Jang Bogo N program, to develop and build its first nuclear-propelled submarines, as part of its drive to better deter regional threats, including those posed by North Korea. In a policy briefing to South Korean President Lee Jae Myung, Cho said the foreign ministry will pursue a foreign policy built on a "virtuous cycle" of self-reliance, alliance and solidarity in the second half. On North Korea, Cho said the ministry will seek ways to lay the groundwork for peaceful coexistence with the North in collaboration with multilateral organisations, like the United Nations. In addition, the ministry will continue working with Washington to revive dialogue with Pyongyang and restart denuclearisation talks through a phased approach, staring with a halt to North Korea's nuclear programs, he said.