WASHINGTON — President Donald Trump said in a Thursday letter that he will raise taxes on imported goods from Canada to 35%, deepening a rift between two North American countries that have suffered a debilitating blow to their decades-old alliance.

The letter to Canadian Prime Minister Mark Carney is an aggressive increase to the 25% tariff first announced by Trump in February, allegedly in an effort to get Canada to crackdown on fentanyl smuggling despite the relatively modest trafficking in the drug. The higher rates would go into effect Aug. 1.

“I must mention that the flow of Fentanyl is hardly the only challenge we have with Canada, which has many Tariff, and Non-Tariff, Policies and Trade Barriers,” Trump wrote.

While multiple countries have received tariff letters this week, Canada — America’s second largest trading partner after Mexico — has become something of a foil to Trump. It has imposed retaliatory tariffs on U.S. goods and pushed back on the president’s taunts of making Canada the 51st state.

Carney was elected prime minister in April on the argument that Canadians should keep their “elbows up.” He has responded by distancing Canada from its intertwined relationship with the U.S., seeking to strengthen its links with the European Union and the United Kingdom.

Hours before Trump’s letter, Carney posted on X a picture of himself with British Prime Minister Keir Starmer, saying, “In the face of global trade challenges, the world is turning to reliable economic partners like Canada.”