Four months since Trump fired the opening salvo of his trade war, only China and Canada have dared to hit back at Washington imposing a minimum 10 per cent global tariff, 50 per cent levies on steel and aluminium, and 25 per cent on autos.

Tariff revenues have brought in more that $113 billion so far this year, according to the Treasury Department data. The U.S. received more than $27 billion in customs duties in June alone.