US President Donald Trump on Thursday unveiled a temporary rollback to steep tariffs targeting Canada and Mexico, providing some reprieve to companies and consumers after blowback on financial markets.

After his sweeping tariffs of up to 25 percent on the two US neighbors took effect on Tuesday, stock markets tumbled, while economists warned that blanket levies could weigh on US growth and raise inflation.

Trump signed orders Thursday to delay fresh levies for Canadian and Mexican imports covered by a North American trade agreement, though he dismissed suggestions that his decisions were linked to market turmoil.

The halt, which lasts until April 2, came one day after the White House announced similar relief for automakers.

Following talks with the "Big Three" US automakers Stellantis, Ford and General Motors, Trump decided to give a one-month exemption on autos coming through the United States-Mexico-Canada Agreement (USMCA).

A White House official told reporters that about 62 percent of Canadian imports will still face the new tariffs, although much of these are energy imports hit by a lower rate of 10 percent.

About half of Mexican imports come through the USMCA.

The latest moves make conditions "much more favorable for our American car manufacturers," Trump said on Thursday.

But he added that major moves would be unveiled on April 2, the date that he has promised "reciprocal tariffs" to remedy practices Washington deems unfair.

At that point, Canadian and Mexican goods could still face levies.

The US president also said he would not modify broad tariffs for steel and aluminum, which are due to take effect next week.

Trump told reporters Thursday in the Oval Office that he had a "very good conversation" with Mexican President Claudia Sheinbaum earlier.

His remarks stood in sharp contrast to the simmering tensions with Canadian Prime Minister Justin Trudeau.

Trudeau said on Thursday that Ottawa will remain in a trade war with Washington for "the foreseeable future" even if there are "breaks for certain sectors." (AFP)