The US is dropping plans for a 10% tariff on certain types of Canadian aluminium that President Donald Trump announced just last month.
The US said it was backing off after determining that imports were likely to decline after an earlier surge.
If the shipments do not fall as expected, officials said they would apply tariffs to the excess.
The reversal comes the same day that Canada was expected to unveil its plans for retaliation.
Canadian leaders said they welcomed the US decision and that, in response, they would suspend the plans to impose tariffs on C$3.6bn ($2.7bn, £2.1bn) in US aluminium products.
"These measures were an error from the very beginning," said Chrystia Freeland, Canada's finance minister. "This is really a day when common sense has prevailed and that's good news."
Ms Freeland described the US move as "unilateral" and Canada had not agreed to abide by any import thresholds. The government remains prepared to retaliate should the US decide to act on its tariff threat, she added.
"After four years of working with this American administration, we have understood that we have to be ready for anything," Ms Freeland said. "We have to expect any possibility and we will continue being ready for any possibility."