“In the past two weeks, the leaders of the two sides have conducted a serious and constructive discussion on properly addressing the concerns of both sides, and agreed to cancel the tariffs by stages in accordance with the development of the agreement,” he said.

Mr. Gao did not specify what tariffs might be dropped, or whether they might consist of higher tariffs Mr. Trump has threatened to impose but not done so yet.

Last month, Mr. Trump announced that the two sides had reached a preliminary trade deal that would involve Beijing buying more farm goods and opening its markets and that he would cancel an Oct. 15 tariff increase. His advisers said they would most likely forgo a December round of tariffs if all went well. But they made no mention of the levies Mr. Trump had already placed on more than $360 billion of Chinese products, including those imposed on Sept. 1 in response to China’s retaliatory tariffs.

Since then, American officials have discussed rolling back those September levies on more than $100 billion of Chinese food, clothing, lawn mowers and other products, according to people briefed on the discussions.

While markets are booming, consumer spending could begin to slump as tariffs hit household goods. And the farm and manufacturing states that supported Mr. Trump in 2016 continue to feel the pinch of his trade war. That is problematic for the president as he campaigns for re-election.

The fight has brought the economies of several farm belt states to a near standstill, data released by the Commerce Department on Thursday showed. From the middle of 2018 through the middle of this year, growth in Iowa, Kansas and Nebraska slowed to less than 1 percent for the year, well below the more rapid expansions they had enjoyed in the first half of 2018.

In the second quarter of this year, which ran from April to June, gross domestic product rose by an annual rate of just 1.1 percent in Wisconsin, Michigan, Iowa, Illinois and Georgia. G.D.P. grew by just 1 percent in Indiana and Kentucky.