Copper surged to a record in New York as reports of halted shipments from Chile intensified a supply squeeze caused by a rush to import the metal into the United States before President Donald Trump slaps the industry with tariffs.

Commodity traders were wrong-footed on Wednesday by a new report that the Trump administration could apply levies on copper imports within several weeks, not later in the year as had been expected by the market. That turbocharged a rally in comex prices to a record $US5.37 a pound.