WASHINGTON—The United States, South Korea and Japan agreed in high-level security talks on Friday to work together to keep up pressure on North Korea to give up its nuclear and ballistic missile programs. In a joint statement after a day of talks, U.S. President Joe Biden’s national security adviser, Jake Sullivan, and his Japanese counterpart, Shigeru Kitamura, and South Korea’s national security adviser Suh Hoon reaffirmed their commitment to address the issue “through concerted trilateral cooperation towards denuclearization.” The three countries also agreed on the need for full implementation by the international community of U.N. Security Council resolutions on North Korea, “preventing proliferation, and cooperating to strengthen deterrence and maintain peace and stability on the Korean Peninsula,” the statement said. The national security advisers also discussed the value of working together to address other challenges such as COVID-19, climate change and promoting an immediate return to democracy in Burma (also …