The main trading partners of the US have reacted angrily after President Donald Trump announced plans to impose tariffs on steel and aluminium imports.
Canada and the EU, both key US allies, said they would bring forward countermeasures.
Mexico, China and Brazil have also said they are weighing up retaliatory steps.
Mr Trump tweeted that the US had been “decimated by unfair trade and bad policy”. He said steel imports would face a 25% tariff, and aluminium 10%.
However, critics argue that the tariffs would fail to protect American jobs and would ultimately put up prices for consumers.
Mr Trump’s announcement hit US markets, with the Dow Jones index closing down 1.7%.
European Commission President Jean-Claude Juncker said the US tariffs would put thousands of European jobs at risk.
In Canada, the largest supplier of steel and aluminium to the US, trade minister Francois-Philippe Champagne said any tariffs would be “unacceptable”.
Minister of Foreign Affairs Chrystia Freeland said Canada would take “responsive measures” if restrictions were imposed but did not give details.
Brazil, also a large steel exporter to the US, threatened “multilateral or bilateral” action to protect its interests.
Germany’s steel industry federation, WV Stahl, said the US measures violated the rules of the World Trade Organization and would have a major impact on Germany’s steel market.
The country which produces more than half the world’s steel gave no immediate official response but there had already been indications it would consider some sort of retaliation.
Little Chinese steel directly reaches US ports because of previous anti-dumping duties, Reuters news agency notes, but US steel industry executives say Chinese steel is still widely shipped to the US through third countries.
President Xi Jinping’s top economic adviser, Liu He, met the Trump administration on Thursday for “frank and constructive” talks, a White House official said.
Mr Trump pledged to rebuild the US steel and aluminium industries which he said had suffered “disgraceful” treatment from other countries, in particular China, for decades.
“When our country can’t make aluminium and steel…you almost don’t have much of a country,” he said.
Mr Trump’s announcement was slightly delayed amid reports of disagreement over the issue among his aides.
More than a dozen metals executives, including representatives from US Steel Corp and Arcelor Mittal, stood alongside him as he made the announcement.
During his presidential campaign, Mr Trump said that foreign countries were “dumping vast amounts of steel all over the United States, which essentially is killing our steelworkers and steel companies”.
Since taking office he has said cheap imports from China are harming the viability of industry in the US.
The US imports four times more steel than it exports and is reliant on steel from more than 100 nations.
The US Department of Energy says the steel industry is recovering after a slump following the 2008 financial crisis.
But it is an industry significantly weaker than it was at the turn of the millennium. In 2000 the US produced 112m tons of steel – a figure that had fallen to 86.5m tons in 2016.
In 2000, 135,000 people were employed in the industry – a figure that fell to 83,600 in 2016.