NO LEADER of a traditional ally has worked harder to conciliate President Trump since the 2016 election than Prime Minister Shinzo Abe of Japan. He has met or conferred with Mr. Trump some 40 times, starting before Mr. Trump’s inauguration in January 2017, and even went so far as to pen a five-page letter nominating the U.S. president for the Nobel Peace Prize, according to news reports, which Mr. Abe has not denied. Cringeworthy as these efforts may seem at times to his countrymen, the Japanese leader’s stroking is pragmatic given his country’s interests. Since the mid-1980s, Mr. Trump has griped, wrongheadedly, about the alleged unfairness whereby this country protects Japanese security while Japan enjoys a merchandise trade surplus with the United States. This is a wild distortion of the true costs and benefits of the U.S.-Japan alliance, which yields huge dividends to this country in terms of geopolitical stability. Yet, given his country’s vulnerability to a nuclear-armed North Korea and China and its dependence on U.S. military backing, Mr. Abe can ill afford to let the mercurial Mr. Trump follow his instincts.

Mr. Abe was back in Washington for yet another encounter with Mr. Trump Friday, with North Korea at the top of the agenda yet again. Even with a more skilled, fair-minded president in charge of the diplomacy, it would be difficult to keep U.S. allies Japan and South Korea, historical rivals, working in concert with Washington against Pyongyang. At the moment, one reason this is even more difficult does, indeed, trace to Mr. Trump’s policies — specifically, launching tariffs and threatened tariffs against Japanese products while withdrawing from the Trans-Pacific Partnership (TPP) trade agreement that the Obama administration had negotiated with Japan and others. This has managed simultaneously to forfeit leverage with China, antagonize Japan and scuttle potential market access for U.S. businesses. Indeed, Japan cut separate deals to allow in more agricultural imports from U.S. competitors, essentially giving them the same terms they and the United States. could have gotten from the TPP.

Removing trade as an irritant in U.S.-Japan relations would help right the geopolitical balance in Asia and refocus the alliance on North Korea. Unfortunately, Mr. Trump made that harder, too, by starting an administrative process whereby the United States could slap 25 percent tariffs on Japanese auto imports, on spurious national security grounds. Mr. Trump has until mid-May to decide whether to impose the levies, which industry experts warn would increase prices for U.S. consumers by billions of dollars while harming Japan’s premier industry.

A way out of the unnecessary clash is clear: Mr. Trump agrees not to impose the tariffs, and Mr. Abe agrees to grant U.S. agricultural producers the same market access other trading partners have gotten. This would require concessions from both leaders — tangible and economic in Mr. Abe’s case, ideological and ego-related for Mr. Trump.

It would seem to be high time for Mr. Trump to facilitate an end to his costly spat with Japan, before Mr. Abe, and his country, conclude that their pragmatic interests might require finding new allies.

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