Washington (AFP) - US President Donald Trump said Friday that he could impose reciprocal tariffs on Canadian dairy and lumber within days – a move set to fuel tensions with Ottawa just days after an earlier wave of levies.

Since taking office in January, Trump has unleashed a series of tariffs and threats targeting US allies and adversaries, including duties of up to 25 percent on imports from Canada and Mexico.

On Thursday, he provided the vital trading partners temporary reprieve, exempting goods coming in from both countries under a North American trade pact.

But he has vowed broader “reciprocal tariffs” as soon as April 2, aimed at remedying practices that Washington deems unfair.

Trump also signaled that reciprocal levies could come as soon as Friday: “Canada has been ripping us off for years on tariffs for lumber and for dairy products.”

“They’ll be met with the exact same tariff unless they drop it, and that’s what reciprocal means,” the president added.

“We may do it as early as today, or we’ll wait till Monday or Tuesday,” he said of the two sectors which have long been affected by trade disputes between the neighbors.

Economists warn that blanket levies could weigh on US growth and raise inflation, adding that they also weigh on business and consumer sentiment.

But Trump kept the pressure up on Canada on Friday: “It’s not fair. Never has been fair, and they’ve treated our farmers badly.”

- Rising tariffs? -

In an earlier interview with Fox Business, Trump said that tariffs affecting Canada and Mexico could rise in the future.

Asked if companies might get more clarity on his trade policies, Trump said: “I think so. But, you know, the tariffs could go up as time goes by.”

White House senior counselor Peter Navarro told CNBC in a separate interview he rejected the idea that there was uncertainty surrounding Trump’s trade policies.

“The uncertainty is created by the fact that people don’t take President Trump at his word,” he said.

Trump’s move to back off some tariffs on Canada and Mexico came after stock markets tumbled as his levies of up to 25 percent took effect this week.

On Thursday, the White House said adjustments exempting goods under the United States-Mexico-Canada Agreement (USMCA) recognize “the unique impact that these tariffs could have on American automotive manufacturers.”

A White House official told reporters that about 62 percent of Canadian imports will still face the fresh levies, though much of them are energy resources slapped with a lower 10 percent rate.

For Mexico, the proportion of imports affected is around 50 percent, the official added on condition of anonymity.

However, Marcelo Ebrard, Mexico’s secretary of economy, said 90 percent of its exports to the United States fall under the three-nation trade pact and will be exempted from tariffs until April.

“Under the agreement, we estimate that we will reach very close to 90%…of all types of products,” he told a press conference.