"Other trading partners observing these threats will have the same mistrust of the negotiation process," experts argue.

President Donald Trump said he was likely to impose tariffs on pharmaceuticals as soon as the end of the month and that levies on semiconductors could come soon as well, suggesting that those import taxes could hit alongside broad “reciprocal” rates set for implementation on Aug.

The European Union has finalized a second list of countermeasures to target US goods worth €72 billion ($84 billion), including Boeing Co. aircraft, automobiles and bourbon if it decides to retaliate as transatlantic trade tensions intensify.

Aircraft, machinery, cars, chemicals and medical devices are the leading big-ticket items on the latest list of U.S. goods the European Commission has proposed to impose tariffs on if talks with Washington do not yield an agreement on trade.