Japan should push back if U.S. President Donald Trump bases trade and other economic policy on "wrong economics," an adviser to Prime Minister Shinzo Abe told Reuters in an unusually direct expression of concern about potential protectionism.

Koichi Hamada, emeritus professor of economics at Yale University and Cabinet adviser, also said Abe could relax his timetable for balancing the budget in the next four years and should be ready to further delay a planned sales-tax hike to ensure economic growth.

Threats by Trump, who took office on Friday, to impose a "border tax" on imports and take other protectionist measures have raised uncertainties about global trade.