All US tariffs will do is alienate its allies

The United States has announced that it will impose tariffs on steel and aluminium imports from the EU, Canada and Mexico. If Britain was outside the EU, perhaps it could have negotiated an exemption. But it isn’t (for now) and thus will be hit by an industrial protectionism that may be popular with Donald Trump supporters but is ultimately self-defeating.

The White House justifies these tariffs on the basis of national security: a country that cannot produce its own steel, goes the argument, cannot defend itself. But a country that slaps tariffs on its allies is also liable to face isolation. The EU says it will sue the US through the World Trade Organisation and impose commensurate tariffs on American imports. Mexico will target a shopping list that includes apples, pork and cheese. What’s deemed good for US industry may turn out to be a nightmare for other sectors.

But will it even help US industry? Unlikely. Cheap imports hurt some domestic producers but also make other businesses viable: the 2.5 million jobs in the US aerospace industry rely on foreign steel and aluminium. Mr Trump wants to trigger a rust-belt renaissance, which is laudable, but a rise in the cost of metals is only going to damage, among others, construction, coal, gas and car makers. When governments pick winners and losers, they pit businesses against each other.

There’s no denying that Mr Trump is addressing a serious problem: the challenge of competing globally when not everyone plays fairly. China is accused of manipulating its currency and stealing intellectual property. America has demanded the EU ease up its tariffs on US cars, pharmaceuticals and agricultural products – and blames European intransigence for its latest action on trade. But putting huge tariffs on foreign goods in revenge is a blunt, old-fashioned instrument that leads to unintended consequences.

Britain should advise the EU to avoid escalation: no one would benefit from a trade war. In Washington, if it enjoys an influence at all, the UK should argue strongly not just for a post-brexit exemption but against protectionism in principle. Yes, some industries are strategically important and the desire to help them is understandable. But this is best done through tax cuts, improving management, pursuing an international level playing field and intervening only when it proves absolutely necessary.