Hours before G7 leaders are set to meet in Quebec for what could be fractious talks about trade, Prime Minister Justin Trudeau said today he didn't pay much attention to U.S. President Donald Trump's recent "quip" about the War of 1812 and British soldiers burning down the White House serving as justification for levying national security tariffs on Canadian steel and aluminum imports.

During a particularly testy call between the two leaders in late May, Trudeau pressed Trump to explain how he could use the national security justification to impose tariffs on exports from a close ally like Canada. In response, Trump said to Trudeau, "Didn't you guys burn down the White House?"

British troops burned down the White House in 1814 during the War of 1812, in retaliation for an American attack on York, Ont., a British colony at the time.

"Obviously I didn't pay much attention to the quip," Trudeau said, smiling, during a stop today in La Baie, Que.

"I focused on the message I was putting out, which was it is inconceivable and quite frankly insulting that the U.S. considers Canada to be a threat to national security.

"This is something that is going to threaten jobs not just in Canada but in the U.S. Workers and consumers are going to suffer because of these wrong-headed tariffs, and that's very much what I was focused on during this conversation."

Prime Minister Justin Trudeau spoke to reporters in La Baie Quebec on Thursday 0:33

Initially, the U.S. exempted Canada, Mexico and the EU from new tariffs on steel and aluminum imports. Trump subsequently rescinded those exemptions as part of his drive to protect U.S. industry from what he claims is unfair foreign competition.

His decision also came after NAFTA renegotiation talks turned sour over disagreements on the auto industry and a sunset clause, among other sticking points.

Now, a 25 per cent tariff will be levied on Canadian steel, while a 10 per cent tariff will be applied to aluminum. In response, Canada slapped the U.S. with $16.5 billion worth of new tariffs on a host of U.S. goods, from lawn mowers to playing cards and felt-tipped pens.

In a January 2018 report prepared by the U.S. Department of Commerce on steel and aluminum imports, the department found that a flood of cheaper foreign imports of these materials has hobbled the U.S. industry — meaning American companies might not be able to respond to procurement requests from the U.S. Department of Defence.

In other words, the Trump administration isn't claiming that Canada poses a physical threat to the U.S. — but is arguing that its cheaper products threaten the continued viability of the U.S. metals industry and its capacity to respond to military demands.

"As steel imports have increased, U.S. steel production capacity has been stagnant and production has decreased," the report reads.

Prime Minister Justin Trudeau walks with U.S. President Donald Trump at the White House in Washington, D.C. on Wednesday, Oct. 11, 2017. Trump has levied tariffs on Canadian aluminum and steel imports. (Sean Kilpatrick/Canadian Press)

"[U.S. Commerce Secretary Wilbur Ross] has determined that the only effective means of removing the threat of impairment is to reduce imports to a level that should, in combination with good management, enable U.S. steel mills to operate at 80 per cent or more of their rated production capacity."

The tariffs were imposed under section 232 of the Trade Expansion Act of 1962. This section has only been used twice before in U.S. history to restrict imports: in 1979 on oil imports from Iran, after that country's theocratic revolution resulted in the storming of the U.S. embassy in Tehran, and in 1982 against similar imports from Libya.

Trudeau has called the use of section 232 "an affront to the … thousands of Canadians who have fought and died alongside American comrades-in-arms."

And, at a separate press conference alongside French President Emmanuel Macron Thursday, Trudeau said he would have a "blunt and frank" exchange with Trump on trade matters while here in Quebec for the G7.

"We will obviously have some very robust discussions on trade ... the role of the G7 is to provide a context to highlight the ways we work together and work through some of the differences and perspectives," he said.