Opposition leaders said Sunday they will do their utmost to ensure the tripartite ruling coalition loses its majority in the House of Councilors in July's election.
Speaking at a television debate program aired by NHK, Yukio Hatoyama, leader of the Democratic Party of Japan, said, "We hope to make the year one during which we will force the administration out of power."
Liberal Party leader Ichiro Ozawa said, "I believe the people will vote to change politics. Opposition forces will be able to gain a majority."
The opposition leaders, however, said it is premature to discuss the feasibility of forming a coalition government among themselves.
"We can discuss a new coalition any time after overwhelming the administration," Hatoyama said.
Meanwhile, Makoto Koga, secretary general of the Liberal Democratic Party, renewed the coalition's resolve to secure a majority during the same program.
The LDP and its ruling allies -- the New Komeito party and the New Conservative Party -- have pledged to keep a majority in the Upper House.
A total of 121 seats in the 247-seat chamber will be at stake. Since 60 Upper House seats held by the coalition are not up for election, the ruling camp will retain its majority if it wins 64 or more seats.