US Secretary of Defence James Mattis has that the increasing nuclear threat from North Korea has brought a new urgency to military and diplomatic collaboration with South Korea. Mattis, while appearing alongside his South Korean counterpart, Song Young-moo, at a press conference in Seoul yesterday, said that the threat from North Korea has grown markedly even since his trip to Seoul earlier this year. <br/><br/>According to CNN, the Secretary said North Korea has accelerated the threat that it poses to its neighbours and the world through its illegal and unnecessary missile and nuclear weapons programmes. Mattis said while diplomacy remains America's preferred course of action, President Donald Trump has made clear that the US commitment to defending US allies and upholding deterrence are "ironclad".<br/><br/>The Pentagon chief made his remarks one day after visiting the demilitarized zone that separates North and South Korea and meeting with South Korean President Moon Jae-in.