Prime Minister Justin Trudeau is expected to speak with President Donald Trump today as Canada's leaders scramble to prepare for a trade war with the United States.

Even as Canada’s prime minister announced more than $100 billion in retaliatory tariffs, he made clear that he was imposing them reluctantly.

Tim McMillan, a former head of the Canadian Association of Petroleum Producers, warned that Ottawa should avoid the temptation to retaliate by cutting off oil supplies from Alberta, which make up half of U.S. oil imports, saying it “would be a huge mistake.”