The outcry among opposition parties over Ryu Matsumoto's comments had threatened to further hinder the unpopular Kan's efforts to pass key bills in a divided parliament as Japan tries to rebuild from the disasters and end a nuclear crisis.

Analysts said the government probably hoped that Matsumoto's quick resignation would avoid further deadlock over a US$25 billion extra budget to aid disaster-hit areas and a compensation scheme for victims of the nuclear crisis at Tokyo

Electric Power's tsunami-crippled nuclear power plant in northeastern Japan. But the furor over Matsumoto, who was also doubling as environment minister, could put added pressure on the prime minister to step down himself.

Kan last month survived a no-confidence vote by pledging to quit but has since blurred the timing of his resignation.