Canada has imposed punitive tariffs worth $2.7 billion (C$3.6 billion) on U.S. exports in retaliation for president Donald Trump re-imposing a 10% tariff on Canadian aluminum exports.

Canada condemned Trump's hasty decision, which reignited his trade war against it, as "unnecessary, unwarranted and entirely unacceptable."

Ottawa's swift riposte came after Trump on Thursday reinstituted the former 10% aluminum tariffs, which were first levied in 2018 on the flimsy grounds that Canadian aluminum still constitutes a threat to U.S. national security.

Trump suspended the 10% aluminum tariffs in May 2019 to secure the Canadian parliament's approval for his new trade deal with Canada and Mexico. The United States-Mexico-Canada Agreement (USMCA) was ratified by the U.S. Senate last January. It went into effect only on July 1 and expires after 16 years.

Deputy Prime Minister Chrystia Freeland said Canada's retaliation was a response to Trump's sudden decision to re-impose the tariffs, which seems to have been triggered by the news that Canada's aluminum exports to the U.S. are on the rise.

Freeland vowed that Canada would espond swiftly and strongly to Trump's renewed hostility. She said Canada will impose dollar-for-dollar countermeasures in a balanced and perfectly reciprocal retaliation. She also said Canada won't escalate but won't back down.

Freeland said Prime Minister Justin Trudeau will spend the next 30 days consulting with Canadian businesses and citizens about the U.S. tariff.

In making his abrupt decision, Trump apparently paid heed to a warning by Secretary of Commerce Wilbur Ross that Canadian aluminum exports to the U.S. had increased substantially in the months after the decision to lift the tariffs in May 2019.

Trump's proclamation re-imposing the 10% tariff alleges the Canadian export surge threatens to harm domestic aluminum production and capacity.

Freeland assailed Trump's reasoning for again imposing the levy. She said the tariffs will hurt American consumers already hard hit by the economic devastation inflicted by the COVID-19 pandemic.

"In imposing these tariffs, the United States has taken the absurd decision to harm its own people at a time when its economy is suffering the deepest crisis since the Great Depression," said Freeland.

She blasted Trump's tariffs as "unnecessary, unwarranted and entirely unacceptable." She said the tariffs shouldn't be imposed. "Let me be clear: Canadian aluminum is in no way a threat to U.S. national security, which remains the ostensible reason for these tariffs, and that is a ludicrous notion."