Donald Trump stepped onto North Korean soil in a historic first Sunday as he met Pyongyang's leader Kim Jong-un in a moment of high diplomatic drama on the world's last Cold War frontier.Moments after becoming the only sitting United States (US) president to set foot inside North Korea, Trump brought Kim back over the dividing line for a meeting where they agreed to start working-level talks on Pyongyang's nuclear weapons.Trump, 73, also said he had invited 35-year-old Kim to t