President Donald Trump said Tuesday he’s imposing a new 50% tariff on all copper imported into the US. However, it’s unclear when the new tariff would take effect. “Today we’re doing copper,” he said at a Cabinet meeting,

The Yale Budget Lab noted that the letters sent Monday would hike the effective tariff rate on U.S. consumers to the highest since 1934.

Copper futures in New York surged after US President Donald Trump said he planned to implement a 50% tariff on imports of the commodity, a move that’s likely to spark massive supply-chain ripples through global metal markets.