The United States will never accept a nuclear-armed North Korea, Defense Secretary Robert Gates warned Wednesday, saying its atomic and missile programmes pose a "lethal and destabilising" threat. "There should be no mistaking that we do not today, nor will we ever, accept a North Korea with nuclear weapons," Gates told US and South Korean soldiers as he began a visit to Seoul. "The peril posed by the North Korean regime remains, and in many ways has become even more lethal and destabilising," he said in a speech.