In the wake of Sunday's poll drubbing, Ishiba said he would stay in office to pursue the tariff agreement and tackle mounting economic problems.

"I can't say until I scrutinise the outcome of the agreement," Ishiba told reporters on Wednesday when asked whether the tariff deal with Washington would influence his decision on whether to stay on.

Ishiba told his close associates on Tuesday evening that he would address his responsibility for the election loss after a trade deal had been reached, the Yomiuri newspaper reported earlier.