U.S. 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 Washington's largest trading partners signaled hope that the trade war would not last long.

U.S. futures markets opened lower in a sign that investors were worried the tariffs could spur inflation and drag on growth, as economists have warned.

Trump, less than two weeks into his second White House term, defended the tariffs as necessary to curb illegal immigration and the drug trade.