The Japanese Communist Party has agreed to withdraw nine candidates from the upcoming House of Councilors election and may hold back at least 11 more in a push by opposition parties to form a united front against the ruling coalition, opposition sources said Sunday.

The party originally planned to field candidates in 30 of 32 single-member electoral districts. With talks underway to unify more candidates, opposition parties may be able to agree to cooperate in 80 percent of the 32 districts, a senior official of the main opposition Democratic Party of Japan said.

Talks between opposition parties accelerated after the JCP agreed to build a unified force against the government of Prime Minister Shinzo Abe on condition that unified candidates call for a scrapping of the new security laws that the JCP and other opponents claim to be unconstitutional.

The laws enacted in September last year mark a change from Japan's exclusively defense-oriented post-World War II security policy, greatly expanding the role the Self-Defense Forces can play when they are sent abroad.

JCP leader Kazuo Shii has said the party will withdraw "a considerable number of its candidates" from the single-member districts, but has not provided a detailed plan.

Half of the 242 Upper House seats come up for election every three years. Of the 121 seats up for grabs, 73 will be filled by winners in single- and multiple-member electoral districts while the remaining 48 are chosen under the nationwide party-list proportional representation system.

Abe's Liberal Democratic Party and its coalition partner Komeito presently control a majority in the Upper House and a two-thirds majority in the 475-seat House of Representatives, the more powerful lower chamber of the Diet.