Leaders of Ishin no To (Japan Innovation Party) and the Democratic Party of Japan agreed Monday to bolster cooperation in the Diet and future elections, with the aim of uniting opposition forces to challenge the ruling camp.

The move by the two largest opposition parties, with Ishin on the verge of breaking up, is likely to accelerate the realignment of the opposition camp ahead of next summer's Upper House election. But it is still unclear whether they can successfully create an opposition bloc powerful enough to face the coalition of Prime Minister Shinzo Abe's Liberal Democratic Party and Komeito, given that there are people in both opposition parties hesitant to work closely together and fear a possible merger.

DPJ President Katsuya Okada and Ishin leader Yorihisa Matsuno said the two parties will set up a framework after the end of the current Diet session in late September for talks about cooperating on elections and various policies.