Donald Trump’s stop-start trade war has sparked big swings across financial markets this year and triggered a sell-off on Wall Street. So investors are waiting nervously for the US president’s “liberation day” on Wednesday, when he has promised to unveil an array of “reciprocal” tariffs on the country’s trading partners.

Equity and bond markets have whipsawed following early announcements on tariffs. Copper has surged in recent weeks as traders have anticipated charges on any imported metal. The gap between the New York Comex and London Metal Exchange prices has opened up to a near record as US inventories have grown.

This past week the US announced the imposition of 25 per cent tariffs on imports of foreign-made cars. Although he has occasionally made conciliatory statements, most recently Trump has promised that these levies will not change. “This is permanent, 100 per cent,” he said after the announcement.