Amid warnings of price increases, Canada moved quickly to retaliate, China said it had planned countermeasures, and Mexico said it would soon unveil its response.

President Donald Trump said on Sunday the sweeping tariffs that he has imposed on Mexico, Canada and China may cause "some pain" for Americans, as Wall Street and the largest U.S. trading partners signaled hope that the trade war would not last long.

Prime Minister Justin Trudeau set out "far-reaching" tariffs of 25%, affecting 155bn Canadian dollars' worth ($106.6bn; £86bn) of American goods ranging from beer and wine, to household appliances and sporting goods.