Japanese Prime Minister Shigeru Ishiba announced his resignation Sunday in order to avoid a split in the ruling Liberal Democratic Party.

His departure plunges Japan, the world’s fourth largest economy and a key U.S. ally, into fresh political uncertainty amid rising living costs, rice policy reforms, growing tensions in the regions, and the impact of U.S. tariffs on its economy.

Since Ishiba took office last year, his LDP-led coalition lost its majority in elections for both houses of parliament amid voter anger over living costs, including an historic defeat in an election for Japan’s upper house in July.

He had faced growing calls to resign, mostly from right-wing opponents within his own party, which has governed Japan for almost all of the post-war era.

Requests for an early leadership election or Ishiba’s resignation gained further traction last week when LDP adopted a review of its upper house loss in July, which called for “a complete overhaul” of the party.

His party were scheduled to vote Monday on holding an early leadership election, a virtual no-confidence motion against Ishiba if approved.

Ishiba finalized details of a trade deal with the U.S. last week, under which Japan pledged $550 billion of investments in return for lower tariffs on its auto sector.