According to the White House, import tariffs on steel and aluminum will increase from 25% to 50%, effective Wednesday. The executive order says the tariff is intended to protect the US’s critical steel and aluminum industries, which have been harmed by unfair trade practices and global overcapacity.

Tariffs on aluminum and steel imported from the UK will remain at 25%, as the two sides continue negotiations on tariffs and quotas under the terms of a previous trade agreement.

Since returning to the presidency in January, Trump has imposed tariffs on both allies and rivals, causing turbulence in financial markets.