TOKYO - Japan's ruling party picks the country's likely next prime minister on Saturday, aiming to regain public trust as voters reeling from rising prices turn to opposition groups promising big stimulus and clampdowns on foreigners.

Farm minister Shinjiro Koizumi, 44, who would be Japan's youngest premier in the modern era, and conservative nationalist Sanae Takaichi, who would be its first female leader, are the frontrunners to lead the Liberal Democratic Party, according to opinion polls.

Also considered a contender is Chief Cabinet Secretary Yoshimasa Hayashi, 64, a centrist party veteran who has held the weighty foreign, defence and agriculture portfolios.

LDP 'ROTTING FROM WITHIN'

The new LDP president is likely to succeed Shigeru Ishiba as prime minister of the world's fourth-biggest economy because the party, which has governed Japan for almost all the postwar period, is the biggest in parliament. But this is not assured as the party and its coalition partner lost their majorities in both houses in the past year.

Various other parties, including the fiscally expansionist Democratic Party for the People and the anti-immigration Sanseito have been steadily luring, especially younger voters, away from the LDP.

Whoever succeeds Ishiba will inherit a party in crisis.

"The LDP is rotting from within, so it's about time for a reset," said Takaichi supporter Osamu Yoshida, 70, speaking outside Shimbashi commuter train station in Tokyo.

Takaichi offers the starkest vision for change, and potentially the most disruptive.

She pledges to jolt the economy with aggressive spending, criticising the Bank of Japan's interest rate increases and raising the possibility of redoing an investment deal with U.S. President Donald Trump that lowered his punishing tariffs in return for Japanese taxpayer-backed investment.

Such a policy shift could spook investors worried about one of the world's biggest debt loads.