In Washington, a federal appeals court agreed to allow Mr. Trump to maintain many of those import duties, which a lower court declared to be illegal in late May. The stay will preserve the centerpiece of the president’s trade agenda while federal lawyers battle with states and businesses that say they were harmed by tariffs that Mr. Trump had no authority to issue.

U.S. officials said the court rulings on tariffs had not come up in the discussions with the Chinese.

It remains unclear whether the latest framework between the United States and China will hold. Henrietta Treyz, director of economic policy at Veda Partners, wrote in a research note that a lot of time in these negotiations was spent “translating, confirming meaning and reiterating framing.” That made negotiations time-consuming but ultimately resulted in keeping “a lot of the status quo, which appears to be what’s come out of London,” she said.