Canada is both the largest source of imported goods to Maine and the state's biggest export market, accounting an estimated $6 billion in cross-border trade last year.

Three of Maine's four members of Congress signed a letter to the Trump administration warning against starting a 'tit-for-tat' trade war with Canada that will cause higher prices for heating fuel, gasoline,

Trump's threats to put tariffs on imports from Canada and Mexico have weighed on markets, even though there has been considerable uncertainty over whether he would make good on his threat.