The Constitutional Democratic Party of Japan and the Democratic Party for the People decided Tuesday that the leader of the new opposition party to be created through their merger will be elected on Sept. 10.
The name of the new party will also be decided on the day. The new party will hold its inaugural convention on Sept. 15.
The schedules were set at a joint meeting among members of the CDP and the DPP, and two groups of independent lawmakers. Before the election, candidates will hold a joint news conference and a debate.
"We hope that the leadership election will boost expectations among the public" for the launch of a large opposition force, CDP Secretary-General Tetsuro Fukuyama told reporters.
The inaugural convention had originally been planned for Sept. 16, but was moved up because the ruling Liberal Democratic Party is considering convening an extraordinary session of the Diet, the country's parliament, on that day.
The Diet session will be held to elect Japan's new prime minister, after current Prime Minister Shinzo Abe announced last week his decision to step down for health reasons.
At a party meeting Tuesday, CDP leader Yukio Edano said, "We'd like to launch the new party in good shape, and change the political situation in the House of Representatives election that will be held in the near future."
Edano is expected to run in the new party's leadership election. He is expected to propose that the party be named Rikkenminshuto in Japanese, the same as the CDP's current Japanese name. He is widely forecast to win the leadership election, and his party name suggestion is expected to be adopted, observers have said.
Among the DPP members, policy chief Kenta Izumi is considering running for the new party's leadership. But Lower House lawmaker Ichiro Ozawa of the DPP told a news conference that the move was "undesirable," given that the lower chamber may be dissolved soon for a snap general election.
Ozawa stressed that Edano should be selected as the new party leader without an election, although sources close to Izumi have said he will run despite Ozawa's comments.
Meanwhile, nine DPP lawmakers backed by labor unions have decided that they will not join the new party, reaching the conclusion in an online meeting between labor unions supporting the DPP and party lawmakers backed by such unions. At the meeting, some participants said that they should join a different new party expected to be established by DPP leader Yuichiro Tamaki, while others said they should watch to see how the situation unfolds.
Also on Tuesday, the Japanese Trade Union Confederation, or Rengo, held an emergency executive meeting. Participants confirmed their support for the new party to be created through the CDP-DPP merger.
"We can't allow our lawmakers to join the party to be set up by Tamaki, who created confusion," Rengo President Rikio Kozu told a news conference, adding that Rengo will not support Tamaki's new party, either.