President Donald Trump cited potential Canadian taxes on U.S. tech companies as his reason for ending trade talks with Canada on Friday.

Trump’s decision is the latest blow to an already strained relationship between the bordering nations. Trump has said the U.S. should annex Canada to improve trade relations and security. Recently elected Canadian Prime Minister Mark Carney has staked his political reputation on pushing back. He has said Canada isn’t for sale.

The president said he would cease negotiations and impose new tariffs because of Canada’s imminent, new digital services taxes.