As trade tensions flared between the world’s largest economies, communication between the United States and China has been so shaky that the two superpowers cannot even agree on whether they are talking at all.

At a White House economic briefing this week, Treasury Secretary Scott Bessent demurred multiple times when pressed about President Trump’s recent claim that President Xi Jinping of China had called him. Although top economic officials might usually be aware of such high-level talks, Mr. Bessent insisted that he was not logging the president’s calls.

“I have a lot of jobs around the White House; running the switchboard isn’t one of them,” Mr. Bessent joked.

But the apparent silence between the United States and China is a serious matter for the global economy.

Markets are fixated on the mystery of whether back-channel discussions are taking place. Although the two countries have not severed all ties, it does seem that they have gone dark when it comes to conversations about tariffs.

“China and the U.S. have not held consultations or negotiations on the issue of tariffs,” Guo Jiakun, a spokesman for China’s foreign ministry, said at a news conference last Friday. “The United States should not confuse the public.”