There is a growing demand for multilateral cooperation in such areas as counterterrorism, climate change, energy, and so on, in spite of increasing ‘My Country First’. The Biden administration is expected to exercise leadership to keep international order more stable. Above all, denuclearizing North Korea and climate change are critical issues that particularly need international cooperation, including China. Faced with unprecedented challenges, South Korea should obtain international support for what South Korea needs in return for its contribution to multilateral cooperation under the US leadership. This should lead to the formation of a Grand National Strategy, which includes denuclearizing North Korea, responding to climate change, and making peace on the Korean Peninsula.