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, adding that he believed the rate will be 50%.

This would mark the fourth across-the-board tariff Trump has imposed during his second term. Currently, most imported cars and car parts face a 25% tariff, while imported steel and aluminum both face 50% tariffs.

The White House didn’t immediately respond to CNN regarding Trump’s timeline for imposing copper tariffs.

Trump ordered a Section 232 investigation into copper imports in February, using a law that gives the president authority to impose higher tariffs based on national security grounds.