Japanese Prime Minister Fumio Kishida on Sunday took a cautious view about acquiring a nuclear-powered submarine to boost the country's defense capability, a call made by some opposition parties ahead of next month's House of Councillors election.

"I'm not so sure if making the leap to a nuclear submarine is a good idea," Kishida said in an appearance on a Fuji TV program with other party leaders, as the official campaigning will kick off Wednesday for the July 10 election.

The premier cited the difficulty of using nuclear power for military purposes under Japan's atomic energy law and the high running cost.

But Kishida, who heads the ruling Liberal Democratic Party, stressed the need to reinforce Japanese defenses at a time when Russia's invasion of Ukraine and China's military assertiveness have highlighted Japan's security challenges.

"We will see what needs to be prioritized to safeguard the people's lives and their livelihoods," he said.

Natsuo Yamaguchi, head of the LDP's junior coalition partner Komeito, echoed Kishida's view, calling the idea of a nuclear-powered submarine "unrealistic."

Ichiro Matsui, leader of the Japan Innovation Party, and Yuichiro Tamaki, head of the Democratic Party for the People, called for the acquisition of a nuclear-powered submarine to boost deterrence and reconnaissance capacity.

Japan "should have an advanced type (of submarine) to increase deterrence," Matsui said, while Tamaki stressed the advantage of a nuclear submarine's ability to stay underwater for months for enhanced surveillance and reconnaissance operations.

Japan is committed to an exclusively defense-oriented policy under the pacifist Constitution, and its defense spending has been limited to around 1 percent of gross domestic product.

The main opposition Constitutional Democratic Party of Japan's leader Kenta Izumi was also against acquiring a nuclear-powered submarine, saying the country's defenses "won't get stronger simply because some deluxe equipment is added."

Among other issues, Kishida reiterated his pledge to implement measures aimed at mitigating the impact of high energy and food prices resulting partly from the yen's weakness, which has raised the cost of imported products.

Kazuo Shii, head of the Japanese Communist Party, urged the government to halve the consumption tax rate to 5 percent and take measures to raise wages.

Rejuvenating the economy hit by the COVID-19 pandemic and accelerating inflation and charting a course for longer-term growth are also expected to be major issues for the upper house race.

The CDPJ and other major opposition parties are also calling for a consumption tax cut. The ruling coalition, meanwhile, see that the current consumption tax rate at 10 percent is needed to finance an aging nation's pension and medical systems.

"We need strong enough wage growth to counter inflation," CDPJ chief Izumi told a gathering on Sunday by a group of business leaders and academics who aim to make policy proposals.

"A consumption tax cut will play a big role in boosting spending," he added.

Separately, Kishida said in the gathering that economic and fiscal policy needs to be guided to gain confidence from financial markets, given that Japan's fiscal health is the worst among developed nations.

Kishida, who is pushing for a new version of capitalism by achieving both economic growth and wealth distribution, stressed the importance of supporting the middle class.

"We have to keep in mind that there is no fiscal restoration unless the economy grows," he said.

In the election for the upper house, in which the coalition currently has a majority, 125 of 248 seats will be contested.

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