China

The clash with Beijing has been Mr. Trump’s biggest trade conflict and the one that has spooked economists and investors the most. It could affect more than $730 billion in goods and services that flow annually between the two countries.

For now, it has no end in sight. Talks broke down in early May after the United States accused China of backtracking from offers made earlier in the negotiations. Mr. Trump then raised tariffs to 25 percent from 10 percent on $200 billion a year in imports from China and threatened to target even more Chinese goods. China soon retaliated and is looking for other ways to strike back. That could mean using the value of its currency as a trade-war weapon or leveraging its hold on key minerals and processes that the world depends on.

The effects could be huge if the trade war lingers or intensifies. American companies count on China for a significant share of their profits and for the critical role it plays in making many of the world’s goods. China needs the American export market to keep its economy going and wants advanced technology like computer chips and software from the United States to foster its economic development.