Ontario is imposing a 25 per cent surcharge on all U.S.-bound electricity as part of its retaliatory measures against U.S. President Donald Trump's tariffs on Canadian goods.

The new levy took effect Monday and will add about $10 per megawatt-hour to the cost of power heading south, the province says. It will generate an estimated $300,000 to $400,000 per day, money that will be used to support workers and businesses hit by U.S. tariffs.

"Believe me when I say I do not want to do this," Ontario Premier Doug Ford said at a news conference Monday.

"I feel terrible for the American people, because it's not the American people who started this trade war. It's one person who's responsible, that's President Trump," he said.