Mr. Trump agreed in Buenos Aires to defer plans to raise tariffs on $200 billion a year in Chinese goods on Jan. 1.

In the United States on Sunday, Robert Lighthizer, the trade representative who is leading the American talks with China, made clear that he considered March 1 “a hard deadline” for the negotiations. “When I talk to the president of the United States, he is not talking about going beyond March,” Mr. Lighthizer said on the CBS program “Face the Nation,” adding, “If there is a deal to be gotten, we want to get it in the next 90 days.”

Mr. Lighthizer also said that the trade talks should not be affected by the arrest of Ms. Meng. “This is a criminal justice matter. It is totally separate from anything that I work on or anything that the trade policy people in the administration work on.”

China’s leaders are coincidentally preparing to observe this month the 40th anniversary of the country’s post-Mao economic overhaul by calling for a series of moves to open up the economy to more trade and foreign investment, people familiar with Chinese policymaking said.

The anniversary, heavily promoted in official propaganda and the subject of Sunday’s conference at Tsinghua University, offers Mr. Xi a chance to take market-opening measures sought by the United States without seeming to give in to American pressure.

The final list of moves is still the subject of considerable discussion within the Chinese bureaucracy. But some options under serious consideration include further reducing tariffs on imports from all over the world and encouraging broader foreign investment in the slowing Chinese economy.

China made some moves in these directions this year, however, and it is unclear how much further the Beijing leadership is willing to go. By Beijing’s calculation, China’s average tariffs have already fallen to 7.5 percent from 9.8 percent at the start of this year. By comparison, average tariffs in the United States are 3.5 percent, while the European Union’s are 5 percent.