By Satoshi Sugiyama and Leika Kihara TOKYO (Reuters) -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.

The reports come after Trump announced a trade deal with Japan, and days after Ishiba's governing coalition lost its majority in the country's upper house.

Japanese voters headed to the polls on Sunday in a tightly contested election amid public frustration over rising prices and the imminent threat of US tariffs. The ruling Liberal Democratic Party (LDP) and its junior coalition partner Komeito need to secure a combined 50 seats to retain an overall majority in the upper house but the latest polling shows they might fall short.