Some key events in Canada-U.S. trade relations since 2018:

Aug. 6, 2020

U.S. President Donald Trump announces plans to reimpose a 10-per-cent tariff on Canadian aluminum, saying "Canada was taking advantage of us, as usual." The tariff had previously been suspended in 2019.

July 1, 2020

The United States-Mexico-Canada Agreement, an update to the North American Free Trade Agreement in place since 1994, takes effect.

Oct. 30, 2019

A U.S. watchdog criticized the way the Trump administration handles taxes on imported steel and aluminum, saying a lack of transparency on the tariffs imposed in March 2018 creates the appearance of "improper influence."

May 17, 2019

Canada and the U.S. reach an agreement that ends the 25 per cent tariff on steel and 10 per cent levy on aluminum that had been in place for most of the previous year. Canada had said the measures stood in the way of ratifying the new NAFTA agreement.

May 31, 2018

The U.S announces tariffs of 25 per cent on imports of Canadian steel and 10 per cent on aluminum to take effect the next day (Canada and the European Union had previously been exempt from wide-ranging protectionist measures launched by Trump; lack of progress in NAFTA renegotiations was cited by Washington as the reason for the tariffs).

In retaliation, Canada later the same day announces plans to impose taxes of up to $16.6 billion on steel, aluminum and hundreds of other products from the U.S.

— With files from The Associated Press

The Canadian Press