Trump's remarks on North Korea could spark Seoul's nuclear rethink / North Korean leader reaffirms policy to 'further' develop nuclear forces / South Korea bristles at Trump calling North Korea 'nuclear power' / DPR Korea's nuclear quest thwarts disarmament efforts, Security Council hears / North Korean leader calls for expanding nuclear forces in face of alleged US threats / North Korean leader calls for expanding his nuclear forces in the face of alleged US threats / South Korea's nuclear fuel goal stirs fears of atomic weapons development / North Korea mocks South Korea's new command, amid rising nuclear debate in Seoul / The UN's nuclear chief says the world needs to pursue dialogue with North Korea over nuclear weapons