Trump’s poor decision on tariffs is part of his overall poor management of the alliance with South Korea:

Yet some trade advisers say the administration is unlikely to consider such an exemption for South Korea, which several officials in the White House see as one of biggest global culprits in trade.

That view has stunned the South Korean government, which is used to working closely with the United States on economic and security matters.

The Trump administration has done a bad job of managing the relationship with Seoul over the last year, and the move to hike tariffs on some of their exports strains that relationship further. Even if the U.S. didn’t need to work closely with South Korea on the standoff with the DPRK, the tariff decision would be a very questionable one, but under the circumstances it is potentially much more harmful. Now that there is a potential opening for talks with North Korea thanks to President Moon’s engagement policy, this is the worst time to widen the rift between Washington and Seoul.

Trump has absurdly dressed up his tariff decision as a matter of national security, but the effect of imposing a higher tariff on South Korean steel will be to undermine the alliance when close cooperation is needed on a major national security issue more than ever. Once again, a bad policy with a spurious national security justification is making it more difficult for the U.S. to work with another government on a real security problem. A trade war with South Korea would be pointless and needlessly destructive at the best of times, but to provoke one in the midst of the standoff with North Korea would be a much worse blunder.

The Trump administration would be smart to shelve trade disputes with South Korea for the time being and focus its efforts on coordinating their approach to North Korea with President Moon. Insofar as there is an opening for diplomatic progress with Pyongyang, it is the result of President Moon’s efforts at engagement. The administration should acknowledge this and avoid taking any actions that harm our ally when they have done valuable work in reducing tensions with North Korea.