TOKYO (Kyodo) -- Prime Minister Shigeru Ishiba on Tuesday called on his fellow ruling party lawmakers to unite toward a key election this summer as the Liberal Democratic Party aims to retain majority control of the House of Councillors with its coalition partner.

The upcoming upper house election will be critical for Ishiba, who heads the LDP, after the ruling coalition lost its majority in the more powerful House of Representatives in a general election last year.

"I want our party to gather all-out efforts and make Japan a better place," Ishiba said at the LDP headquarters as party lawmakers returned to work for the new year.

In the election, which must be held by late July and in which only half the seats will be contested, the LDP and its coalition partner Komeito party aim to retain their majority of the 248-member upper house, Secretary General Hiroshi Moriyama, the No. 2 of the ruling party, said at a press conference the same day.

Moriyama said the coalition hopes to retain majority control of the upper house "at all costs," adding that it is also important to win at least half of the contested seats.

Ishiba's minority government is set to seek parliamentary approval of a state budget for the next fiscal year, which will begin in April, during a 150-day regular Diet session from late January.

In Japan, the lower house is more powerful because it can override the upper house when they are not in agreement over budgets, laws and other critical issues.

Opposition parties that secured a bigger say in the lower house after the general election in October want to curb the influence of the ruling coalition in the upper house.

Yoshihiko Noda, head of the Constitutional Democratic Party of Japan, has said the main opposition party will do all it can to prevent the ruling coalition from grabbing half of the seats up for grabs.