The loss on Sunday left the Liberal Democrats a minority party in both houses of Parliament, while two new nationalist parties surged.

Japan's far-right populist Sanseito party was one of the biggest winners in the weekend's upper house election, attracting many voters with its "Japanese First" platform.

Japanese Prime Minister Shigeru Ishiba will announce his resignation by the end of next month, Japanese media reported on Wednesday, following a bruising election defeat that cost his administration its upper house majority.

After months of fraught negotiations with the United States, Japan clinched a deal just days before punitive tariffs were scheduled to take effect.

The Sanseito party tapped into discontent over issues galvanizing voters worldwide: inflation, immigration and a political class dismissed as out of touch.

The road to Japan’s trade deal with the U.S. just got longer and more winding as Prime Minister Shigeru Ishiba’s coalition lost its majority in the upper house following the election held on Sunday. It was only in late October that Ishiba’s Liberal Democratic Party lost the majority in the lower house it had held since 2012.

The fringe far-right Sanseito party emerged as one of the biggest winners in Japan's upper house election on Sunday, gaining support with warnings of a "silent invasion" of immigrants, and pledges for tax cuts and welfare spending.