Since taking office, President Donald Trump has been growling loudly about taking on trade miscreants whose companies’ exports cheat their way into the US market. Soon, he will have to decide how hard to bite.

Mr Trump’s administration has been threatening for some time to invoke a US law to protect national security to block imports of steel, saying that dependence on imported raw materials threatens US stability. Few doubt that China, his administration’s trade bugbear, is the main target. The decision has been delayed: unprecedented warnings from fellow Nato members that such restrictions would threaten their own security perhaps have given the White House some pause.

If the administration cares about preserving open trade and good relations with its allies, it should abandon its plans altogether. Wholesale restrictions on imports of raw materials with a spurious national security justification are economically nonsensical and politically ruinous.