Theresa May has welcomed the temporary exemption of EU steel and aluminium from US import tariffs.
The White House said on Thursday that the European Union, Canada, Mexico, Australia, Argentina, Brazil and South Korea will be free from the levies announced by Donald Trump.
The exemptions will last until May 1, pending further discussions, while tariffs on other countries will come into effect on Friday.
President Trump signed an order that paves the way for imposing tariffs on as much as $60 billion worth of Chinese imports.
The move was designed to punish Beijing for what Mr Trump said is the theft of American technology and Chinese pressure on US companies to hand it over.
"It is the largest deficit of any country in the history of our world," Mr Trump said of the US-China trade imbalance, blaming it for lost American jobs.
China has already warned that it will take "all necessary measures" to defend itself, raising the prospect of a trade war between the world's two biggest economies.
Mr Trump threatened to impose punitive tariffs on steel imports to the US, but the EU is exempt from any such move for now and Mrs May will be discussing with fellow EU leaders how the exemption can be made permanent.
The prime minister dropped plans to fly home from the European Council summit in Brussels overnight in order to stay on for discussions on the development with fellow EU leaders.
Arriving at the summit on Friday, Mrs May said: "We have been working very hard to secure an EU-wide exemption to the steel tariffs that the Americans have announced.
"I am pleased that they have announced a temporary exemption for the EU. What I will be working with my fellow EU leaders today on is to see how we can secure a permanent exemption for the EU from these steel tariffs.
"We will be talking about what the next steps might be. I have stayed on to talk about these next steps because the steel industry is hugely important to the UK and the British Government and I want to ensure that steel workers and their jobs are properly safeguarded."