The International Monetary Fund (IMF) has joined criticism of US President Donald Trump's plan to impose a 25 per cent tariff on steel imports and 10 per cent on aluminium.
The body warned that such a move would hurt the US, as well as other countries, the BBC reported.
It said others could follow Trump's precedent by claiming tough trade restrictions were needed to defend national security.
Canada, the largest supplier of steel to the US, said tariffs would cause disruption on both sides of the border, the BBC report added.
It is one of several countries that have said they will consider retaliatory steps if the president presses ahead with his plan next week.
EU trade chiefs are reportedly considering slapping 25 per cent tariffs on around $3.5bn of imports from the US.
World Trade Organisation Director General Roberto Azevedo said: "A trade war is in no one's interests."