Donald Trump's trade advisers were finalizing plans on Wednesday for the reciprocal tariffs the U.S. president has vowed to impose on every country that charges duties on U.S. imports, ratcheting up fears of a widening global trade war and threatening to add to already-sticky U.

Senior aide Peter Navarro is a driver of the idea inside the White House. He pushed for reciprocal tariffs during Trump’s first term.

President Donald Trump’s desire to get even on countries by matching tariffs they have on American goods could come at a steep cost.