The possibility that former U.S. President Donald Trump will return to the White House is raising concerns among Japanese companies that his administration may pursue greater protectionism, including raising tariffs, and undo President Joe Biden's efforts to reduce carbon emissions.

Trump's return "would mean another tariff war," said Takeshi Niinami, CEO of beverage company Suntory Holdings.

Trump has already said that he would impose a 10% tariff on all imported products and a 60% tariff on imports from China.