The announcement means fresh uncertainty for the world’s fourth-largest economy as it battles rising food prices and deals with the fallout of US tariffs on its vital auto sector.

Ishiba told a news conference that the long-dominant Liberal Democratic Party (LDP) should prepare for a leadership election, and he would stay in position until then.

“Now that negotiations on US tariff measures have reached a conclusion, I believe this is the appropriate moment,” he said.

“I have decided to step aside and make way for the next generation,” said the 68-year-old.

US President Donald Trump signed an order on Thursday to lower tariffs on Japanese autos, with Washington finally moving to implement a trade pact negotiated with Tokyo in July.

However, although Japanese autos will now face a 15 percent tariff instead of the current 27.5 percent, the levy will still cause significant pain in the crucial industry.

Seen as a safe pair of hands, Ishiba took the helm of the LDP in September 2024 and became the 10th man in the party to serve as prime minister since 2000.

“We have switched prime ministers many times,” said 25-year-old Yuri Okubo, speaking from a Tokyo park on a hot afternoon.

“I’m worried that no matter who the new prime minister will be, nothing will change.”

Mounting resignation calls

Opponents of Ishiba had been calling for him to step down to take responsibility for dire election results, following the party’s poor performance in an upper chamber vote in July.

Lower house elections in October 2024 saw the LDP suffer its worst result in 15 years.

Media reports said earlier that Ishiba wanted to avoid a split in the party and that he was unable to withstand the mounting calls for his resignation.

The farm minister and a former prime minister reportedly met with Ishiba on Saturday night to urge him to resign voluntarily.

Four senior LDP officials, including the party’s number two Hiroshi Moriyama, offered to resign last week.

Ishiba’s term as party leader was supposed to end in September 2027.

“While striving to accommodate many people and foster harmony, my sincere efforts resulted in losing my particular path,” Ishiba said, adding he would not run in the leadership race.

His most prominent rival, hardline nationalist Sanae Takaichi, was the runner-up in the last leadership election and all but said on Tuesday that she would seek a contest.

A Nikkei survey held at the end of August put Takaichi as the most “fitting” successor to Ishiba, followed by farm minister Shinjiro Koizumi, but 52 percent of respondents said a leadership contest was unnecessary.

After the July election, social media users called for the moderate Ishiba to remain in power under the hashtag “#Ishiba Don’t quit”.

The LDP has governed almost continuously since 1955, but voters have been deserting the party, including towards fringe groups such as the populist Sanseito.

Factors include rising prices, notably for rice, falling living standards, and anger at corruption scandals within the LDP.

Ishiba, a diligent career politician, was elected LDP leader last year on his fifth attempt, promising a “new Japan”.

Both China and South Korea welcomed his appointment then, hoping for improved ties.