In a series of posts on his Truth Social platform late Monday, the president-elect warned he would impose trade barriers on the top three US trading partners the day he takes office.

China quickly responded Tuesday that "no one will win a trade war," while Mexican President Claudia Sheinbaum said that tariffs were "not acceptable" and no way to address immigration and drug problems.

A Canadian government source said Prime Minister Justin Trudeau called Trump and had a "productive" discussion, without giving further detail.

Trump's posts signaled he intends to return immediately to the style of his first presidency, when he regularly shocked Washington and US partners around the world with major policy shifts announced at odd hours on social media.

If enacted, the tariffs would spark disruption across the global economy, deepening tensions with US rival China and upending relations with the two huge US neighbors.

However, the threat backs up one of Trump's main promises in his campaign against Democrat Kamala Harris, which was to use US economic muscle as leverage on issues having little to do with trade -- namely his claim that the United States is under siege by foreign crime and dangerous migrants.

"On January 20th, as one of my many first Executive Orders, I will sign all necessary documents to charge Mexico and Canada a 25 percent tariff on ALL products coming into the United States," Trump posted.

"This Tariff will remain in effect until such time as Drugs, in particular Fentanyl, and all Illegal Aliens stop this Invasion of our Country!" he said. "We hereby demand that they use this power, and until such time that they do, it is time for them to pay a very big price!"

In another post, Trump said he would also be slapping China with a 10 percent tariff, "above any additional Tariffs," because the world's second biggest economy was failing to execute fentanyl smugglers.

"Representatives of China told me that they would institute their maximum penalty, that of death, for any drug dealers caught doing this but, unfortunately, they never followed through," he said.

Liu Pengyu, a spokesman for China's embassy in the United States, told AFP that "China believes that China-US economic and trade cooperation is mutually beneficial in nature."

Mexico's Sheinbaum fired back at Trump, saying his tariffs diplomacy was misguided.

"President Trump, it is not with threats or tariffs that the migration phenomenon will be stopped, nor the consumption of drugs in the United States," she told reporters, reading a letter she will send to Trump in which she proposes dialogue.

"It is not acceptable and would cause inflation and job losses in the United States and Mexico," she said.

- Bluster or serious? -

William Reinsch, senior adviser at the Center for Strategic and International Studies, said Trump's Truth Social threats may be bluster -- a strategy of "threaten, and then negotiate."

However, Trump's first term in the White House was marked by an aggressive and protectionist trade agenda that also targeted China, Mexico and Canada, as well as Europe.

While in the White House, Trump launched an all-out trade war with China, imposing significant tariffs on hundreds of billions of dollars of Chinese goods.

China responded with retaliatory tariffs on American products, particularly affecting US farmers.

Economists say tariffs can hurt US growth and push inflation, since they are primarily paid by importers bringing the goods into the United States, who often pass those costs on to consumers.

Trump has said he will put his commerce secretary designate Howard Lutnick, a China hawk, in charge of trade policy.

Lutnick has expressed support for a tariff level of 60 percent on Chinese goods alongside a 10 percent tariff on all other imports.