SEOUL, South Korea (AP) — North Korean leader Kim Jong Un has called for waging what he called another arduous march to fight severe economic difficulties, for the first time comparing them to a 1990s famine that killed hundreds of thousands. North Korea monitoring groups haven’t detected any signs of mass starvation or a humanitarian disaster. But Kim’s comments suggest how seriously he views the current difficulties, which foreign observers say are the biggest test of his nine-year rule. Chinese data show North Korea’s trade with China, its biggest trading partner and aid benefactor, shrank by about 80% last year following North Korea’s border closure as part of stringent pandemic measures. South Korea says there are signs the North is easing border controls.