Donald Trump's trade and manufacturing adviser says the U.S. president's planned tariffs for steel and aluminum imports would not immediately apply to Canada and Mexico.

Peter Navarro told Fox Business on Wednesday evening that Trump intends to sign a proclamation including such a clause favouring the two neighbouring countries.

Navarro said the tariffs would go into effect within 15 to 30 days.

Trump tweeted about the matter early on Thursday morning.

White House press secretary Sarah Huckabee Sanders told reporters on Wednesday that exemptions to the proposed tariffs would be made on a "case-by-case" and "country-by-country" basis, a reversal from the policy articulated by the White House just days ago that there would be no exemptions from Trump's plan.

This was excerpted from the 8 March 2018 edition of CBC News.