Japan's Prime Minister Naoto Kan speaks during a debate with the main opposition Liberal Democratic Party leader Sadakazu Tanigaki (not in the picture) at the parliament in Tokyo June 1, 2011. Rebels in Kan's party on Wednesday cranked up pressure on the unpopular leader as he struggled with a nuclear crisis, threatening to back an opposition-sponsored no-confidence motion if he refused to step down. REUTERS/Kim Kyung-Hoon (JAPAN - Tags: POLITICS)