The House of Representatives endorsed a proposal Tuesday to keep the Diet open through July 28 in a vote that was backed by the Liberal Democratic Party-New Komeito ruling bloc.
The Democratic Party of Japan and three other opposition parties voted against the 55-day extension. The Diet was scheduled to close after Wednesday's session.
Prime Minister Taro Aso is expected to dissolve the Lower House during the extended session to call a general election by or on Sept. 6, which is the last Sunday before Sept. 10, when the current terms of Lower House politicians expire.
The most unlikely dates are Aug. 9, the anniversary of the U.S. atomic bombing of Nagasaki, and the following two Sundays, when the public will be busy with the Bon holidays.
Aso is expected to push for early August because New Komeito wants the election held at least a month from the Tokyo Metropolitan Assembly race on July 12.
Aso has said he will decide the timing after taking into account "various matters," which will probably include how the DPJ acts in the Diet and how he does in opinion polls.
By extending the Diet session, Aso is hoping to get the extra budget bills for fiscal 2009 and other key legislation cleared. Among the key items will be the antipiracy bill, a bill to reform the national pension plan and one to reform the tax system.
New Komeito wants to concentrate on the metro assembly poll because Tokyo is the major power base for the party.
