The US has doubled tariffs on foreign steel and aluminum imports to 50 per cent, pressing ahead in the face of criticism from key trading partners with a measure that Donald Trump says is intended to revive the American industry.

The president has ratcheted up the rate on foreign metals to 50 percent, double the previous rate, saying the levies weren’t high enough to help the U.S. industry.

US President Donald Trump has signed an order doubling tariffs on steel and aluminium imports from 25% to 50%. The move hikes import taxes on the metals - key inputs in everything from cars to canned food - for the second time since March.