Trump sent letters to several major economies outlining trade tariffs against them at the start of the week, while also postponing the effective date of his tariffs to August 1 from July 9.

He insisted at a cabinet meeting on Tuesday that the new deadline will not be pushed back any further, after stating earlier this week that it was “not 100% firm.” He added that negotiations are going well with the European Union and China, but flagged that the EU is days away from receiving its own tariff letter.

The president also raised the prospect of a 50% tariff on imported copper, in the latest sign that his aggressive trade agenda involves not just countries, but specific sectors as well. Copper is a particularly crucial metal who uses apply to vehicle production, military hardware, power grid infrastructure and more.

Other levies on everything from pharmaceuticals to semiconductors could soon be unveiled, Trump suggested.