The formal step was to be taken Friday with an election set for Dec. 16, The Japan Times reported.
The Democratic Party of Japan has governed the country for the past three years. Experts predict the Liberal Democratic Party, which has ruled the country almost continuously since World War II, will return to power.
Noda was under pressure from both inside and outside the DPJ, the Times said.
Six DPJ members of Parliament have said they are leaving the party this week, enough to leave the governing coalition without a majority and the prime minister vulnerable to a no-confidence vote.
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