The main opposition parties have decided to field single candidates in most one-seat districts in this summer's Upper House election to more effectively face off with ruling party candidates, their members said Wednesday.

Under the agreement involving the Constitutional Democratic Party of Japan, the Democratic Party for the People and the Japanese Communist Party, the parties have agreed to cooperate in 30 out of the 32 constituencies where one seat will be contested. In 14 of the 30 districts, the parties have agreed not to run against independent candidates.

"We are taking an important step toward toppling the government (of Prime Minister Shinzo Abe)," Yukio Edano, leader of the CDP, told reporters after a meeting of the opposition forces.