Donald Trump has risked a transatlantic trade war by revealing he will impose a 25 per cent tariff on all steel imports in a move that could have a “devastating” impact on the UK industry.

The US president's move spooked investors, with stock markets in Asia on Friday extending a Wall Street rout.

Mr Trump said he planned to make the announcement next week and also said there would be a 10 per cent tariff on aluminium..

It came despite fierce lobbying from British cabinet ministers and officials as well as infighting among senior Trump administration figures over the repercussions.

Is is not clear whether the tariff will be put on all global steel imports - hitting the UK - or just on a select number of countries including China and India.

The tariff amounts to one of the biggest pieces of trade protectionism adopted since Mr Trump took office and could trigger barriers being raised by those countries affected.

Mr Trump said on Thursday the tariff would be put in place “for a long period of time” but did not go into specifics.