President-elect Donald Trump said on Monday he will impose a 25% tariff on all goods from Mexico and Canada and an additional 10% tariff on Chinese goods, effective from his first day in the White House.

“On January 20th, as one of my many first Executive Orders, I will sign all necessary documents to charge Mexico and Canada a 25% Tariff on ALL products coming into the United States, and its ridiculous Open Borders,” he wrote on Truth Social. “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 went on to say his punitive tariffs on China were also linked to his concerns with fentanyl, accusing the country of not following through on instituting severe penalties — including the death penalty — on drug importers.

“They never followed through, and drugs are pouring into our Country, mostly through Mexico, at levels never seen before,” Trump wrote. “Until such time as they stop, we will be charging China an additional 10% Tariff, above any additional Tariffs, on all of their many products coming into the United States of America. Thank you for your attention to this matter.”

Trump has long advocated for sharp tariffs on imports — effectively, a fee on foreign products brought into the country — to help American manufacturers. But many economists say those plans will likely make inflation worse and increase costs for U.S. businesses and consumers alike. They’re also very likely to be seriously damaging to many of America’s major trading partners.

The president-elect has claimed foreign companies will pay the brunt of those additional costs. But U.S. companies would pay more to import goods, and studies on similar tariffs imposed during Trump’s first term found most of those increased costs were passed on to American consumers.

The Associated Press also notes that tariffs weaken competition from foreign goods, so manufacturers in the U.S. are able to raise their own prices in return.

Businesses have already warned about the potential impacts of Trump’s plans. The chief financial officers of Walmart and Lowe’s recently said prices will probably go up in the near future.

Trump suggested the tariffs would force countries to resolve several of the topics he made central to his campaign: Undocumented migrants crossing the U.S. border and the fentanyl crisis. He claimed that Mexico and Canada could “easily solve” those longstanding issues.

“Both Mexico and Canada have the absolute right and power to easily solve this long simmering problem,” he wrote Monday. “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!”

This is a developing story. Please check back for updates.