Taking questions during a joint news conference with President Jair Bolsonaro of Brazil, Mr. Trump talked repeatedly about the Xi meeting, while avoiding specific predictions. “At a minimum, it will be productive — we’ll see what happens and what comes out of it,” Mr. Trump said.

He denied recent news reports that he had promised not to impose any new tariffs on China in order to arrange his meeting with Mr. Xi on Saturday. “No, I didn’t promise,” he said.

Mr. Trump’s senior aides have just gone through the necessary legal steps for him to impose tariffs of up to 25 percent on $300 billion a year worth of American imports from China. But they have not given any timetable for when he might actually do so.

Mr. Trump tried to portray the overall trade war as likely to end well. “I think we have a very good chance, we’ll see what happens,” he said.

But China is looking for other options.

In the latest sign that China is seeking alternatives to its reliance on exports to the United States as the trade war continues, a Chinese official said on Friday that it hoped to accelerate talks this year on a regional free trade agreement for East Asia, South Asia and the southern Pacific.