Trump's 25% steel, aluminum tariffs add on to Canada and Mexico duties: W.House

US President Donald Trump's planned 25-percent tariffs on all steel and aluminum imports will stack on the hefty duties earlier announced on Canada and Mexico, a White House official told AFP Wednesday.

Trump had in early February unveiled sweeping tariffs of 25 percent on Canadian and Mexican goods, with a lower rate of 10 percent on Canadian energy imports.

But shortly after making that announcement, he halted the blanket levies on the United States' immediate neighbors for a month as both countries vowed to step up measures against illegal immigration and fentanyl smuggling.

If those tariffs are reimposed at the end of a 30-day deadline, the levies on Canadian and Mexican steel and aluminum could hit 50 percent, the official said, speaking on condition of anonymity.

Canadian Prime Minister Justin Trudeau and Mexican President Claudia Sheinbaum struck deals for a postponement, following calls with Trump just hours before the US tariffs were due to take effect.

But while talks between the North American trading partners continued, Trump signed separate orders to impose 25-percent tariffs on steel and aluminum imports from March 12, widening a trade war despite warnings from other countries.

Canada and the European Union have since vowed to stand firm against Trump's latest salvo on steel and aluminum.