The president said Mexico and Canada have failed to curb the flow of drugs into the U.S. after giving the countries 30 days to do so before enacting the tariffs.

Over $200 billion in trade is carried by freight rails between the US, Canada and Mexico, with auto parts, oil, lumber, ag, and chemicals linking the economies.

As traders worldwide wait to see if U.S. President Donald Trump once again holds off on putting new tariffs on Canada and Mexico, the head of the U.S. Treasury Department has highlighted one potentially promising avenue for America’s neighbors.