Japan's top forex diplomat has escalated warnings against a weaker yen, as Donald Trump's victory in the U.S. presidential election intensifies uncertainties for the Bank of Japan (BOJ). The yen's weakening has prompted Japan’s chief currency official to caution that authorities will take appropriate action against excessive currency moves. Despite the uncertainties surrounding Trump's policies, BNP Paribas economist forecasts that the BOJ is still expected to raise interest rates in December. Analysts argue that Trump's victory could lead to higher interest rates in Japan. The Bank of Japan faces heightened risks as the yen renews its slide, according to an ex-official.