Trump: "When a country Taxes our products ,at say 50%, and we Tax the same product coming into our country at ZERO"

[chuck norris 42]

 I was surprised by the following tweet by the president 

"When a country Taxes our products coming in at, say, 50%, and we Tax the same product coming into our country at ZERO, not fair or smart. We will soon be starting RECIPROCAL TAXES so that we will charge the same thing as they charge us."

What countries is he talking about ?