The uncertainty is weighing on the United States economy, particularly manufacturing, which has slumped over the past several months. Chinese economic growth has slowed to its lowest rate in nearly three decades, while Germany has barely avoided falling into recession.

“It’s striking that in almost every corner of the world geopolitical tensions are threatening to put the brakes on growth,” John Williams, the president of the Federal Reserve Bank of New York, said in a speech last week. “The uncertainty created by current events is no doubt having a lasting effect on the economic conditions we’re experiencing today.”

Mr . Trump’s theatrical embrace is not limited to China. He has injected similar drama into trade talks with other partners, including Europe, Japan, Canada and Mexico, publicly threatening them with tariffs and suggesting he might leave some trading partners behind.

The president says his approach has created leverage — and in some cases, he is right. The threat of tariffs has prompted officials from Mexico, Canada, Japan and elsewhere to make concessions they might not otherwise have agreed to. It has also brought China, which is heavily reliant on exports to the United States, to the negotiating table.

But that strategy may now be discouraging China from bringing the talks to a close. Mr. Trump’s tendency to waver and increase his demands have made China wary of offering concessions, for fear that he will only demand more, people familiar with Chinese trade policy said.

Eswar Prasad , a trade professor at Cornell, said the president’s “mercurial temperament and predilection to undercutting his own negotiating team” had complicated the already challenging task of striking a deal. “By hyping up expectations and setting unrealistic goals for the trade talks, Trump makes the prospects for any sort of trade deal with China more uncertain and volatile,” he said.

The two sides have been unable to reschedule a meeting between Mr. Trump and his Chinese counterpart, Xi Jinping, in Chile that was canceled because of domestic protests. Mr. Trump has since said that a deal signing would take place in United States “farm country,” but the Chinese have been reluctant to commit to a meeting until a deal that includes tariff reductions is finalized.