Yet there is one little saving grace here: This will upset China.

While China’s aluminum and steel export share in the U.S. market is limited, it is a factor in Beijing’s consideration. In that sense, if Trump is willing to thread these tariffs into his North Korea strategy, he might be able to get Beijing to cut off its export and financial capital flows to North Korea. As we’ve explained, the only way to pressure Pyongyang is for Trump to pressure its key benefactor, China, far more substantially.

Why would increased Chinese pressure on Kim Jong Un’s regime be so valuable?

Because if China cuts off its lifelines to Kim, Kim will have no choice but to come crawling to the negotiating table.