Donald Trump's proposed hike in steel tariffs will have a "significant impact" on the UK, the industry trade body has warned.
The US President has set out plans for steel imports to face a 25% tariff and aluminium 10%.
Richard Warren, head of policy at UK Steel, said the US was a significant export market for British producers.
"It would have a significant impact if it did go ahead," he told BBC Radio 4's Today programme.
Mr Trump said US steel and aluminium had been "decimated" by "unfair" trade policies, and insisted he would not let America be "taken advantage of any longer".
Further details on the plans are expected next week.
Mr Warren said the US was a "fairly significant" market, accounting for around 15% of UK steel exports.
"At the minute we don't know exactly how these tariffs will be implemented, so we'll have to wait until the official announcement next week," he said.
"But the assumption, from what he said, is that it would be a blanket tariff of 25% on all steel products.
"It's very big, considering the thin margins that larger steel operators will be operating to - 25% is a significant tariff."
The European Union has indicated it could retaliate, potentially starting a trade war with the US.
European Commission president Jean-Claude Juncker said: "We will not sit idly while our industry is hit with unfair measures that put thousands of European jobs at risk.
"I had the occasion to say that the EU would react adequately and that's what we will do.
"The EU will react firmly and commensurately to defend our interests. The Commission will bring forward in the next few days a proposal for WTO-compatible counter-measures against the US to rebalance the situation."