US PRESIDENT Donald Trump signed an order imposing stiff tariffs on imports from Canada, Mexico and China at the weekend, triggering a trade war as the three countries swiftly retaliated.

The Republican president claimed on social media that the tariffs, which take effect tomorrow, were necessary “to protect Americans,” as he pressed all three nations to curb the manufacture and export of illicit drug fentanyl and for Canada and Mexico to reduce illegal migration into the US.

The tariffs, if sustained, could cause domestic inflation to significantly worsen, threatening to derail Mr Trump’s pledge of bringing down the cost of groceries, petrol, housing, cars and other goods. They also risk throwing the global economy into turmoil just two weeks into his second term.

Mr Trump declared an economic emergency in order to place duties of 10 per cent on all imports from China and 25 per cent on imports from Mexico and Canada.

Energy imported from Canada, including oil, natural gas and electricity, would be taxed at a 10 per cent rate. Mr Trump’s order also includes a mechanism to escalate the rates charged by the US against retaliation by the other countries.

“The actions taken today by the White House split us apart instead of bringing us together,” Canadian Prime Minister Justin Trudeau said as he announced that his country would put matching 25 per cent tariffs on up to $155 billion (£77.6bn) in US imports, including alcohol and fruit.

Mexican President Claudia Sheinbaum also ordered retaliatory tariffs.

“We categorically reject the White House’s slander that the Mexican government has alliances with criminal organisations, as well as any intention of meddling in our territory,” she wrote in a post on X.

Ms Sheinbaum said she had instructed her economy secretary to implement retaliatory tariffs and other measures in defence of Mexico’s interests.

“If the United States government and its agencies wanted to address the serious fentanyl consumption in their country, they could fight the sale of drugs on the streets of their major cities, which they don’t do — and the laundering of money that this illegal activity generates that has done so much harm to its population.”

China’s Ministry of Foreign Affairs said the government “firmly deplores and opposes this move and will take necessary countermeasures to defend its legitimate rights and interests.”

Beijing made fentanyl-related drugs controlled substances in 2019 and conducted “counternarcotics co-operation with the US,” the ministry said.

China’s Ministry of Commerce warned that it would file a lawsuit with the World Trade Organisation against the “wrongful practices of the US” and take measures to safeguard its rights and interests.