SEOUL, South Korea — Taking an unprecedented step onto North Korean soil, President Donald Trump announced Sunday that Washington and Pyongyang will relaunch stalled nuclear talks during an extraordinary last-minute meeting with Kim Jong Un. Side-by-side with Kim in the heavily-fortified demilitarized zone, Trump became the first sitting U.S. president to cross the 1953 armistice line separating North and South Korea, then joined Kim for a roughly 50-minute meeting.