It’s easy to sell soybeans to China. The Chinese are voracious consumers of the world’s raw materials. Until 2018, shiploads of soybeans from the American Midwest streamed to the processing plants that dot the Chinese coast. So there is no reason to applaud the news that the Chinese government has offered to guarantee large purchases of American soybeans as part of a potential trade deal with the United States that the Trump administration is pushing to complete by late March or early April.

Instead, it is a worrying sign that the administration may settle for an ephemeral victory at the expense of America’s long-term economic interests.

President Trump, by imposing tariffs on Chinese imports, created an opportunity to improve America’s economic relationship with China. It is a chance that may not come again. The American economy is strong, while the Chinese economy is faltering. China still needs American technologies. And despite Mr. Trump’s distaste for multilateralism, much of the rest of the world shares his concerns about China’s economic policies and trade practices.

His decision to go it alone, rather than making common cause with longstanding allies, was ill advised, and his tit-for-tat trade war has caused significant pain for many Americans. Farmers and other American exporters lost access to an important market; consumers are paying higher prices on a wide range of goods.