U.S. citizens walk out from Sendai City Hall, as they prepare to evacuate on a bus organised by the U.S. embassy for the citizens in Japan in Sendai, northern Japan March 19, 2011. Japan's unprecedented multiple crisis of earthquake, tsunami and radiation leak has unsettled world financial markets, prompted international reassessment of nuclear safety and given the Asian nation its toughest time since World War Two. REUTERS/Yuriko Nakao (JAPAN - Tags: DISASTER ENVIRONMENT)