Mr. Trump has often weighed in at the last minute to change the terms in past negotiations, imposing tariffs or lifting sanctions based on personal conversations with foreign leaders or perceived compliments or slights.
“The president has undercut, privately or publicly, every one of his trade representatives,” said William Reinsch, a former United States trade official and now a senior adviser at the Center for Strategic and International Studies. “The president is his own trade representative and he’s going to make the decisions.”
In the Oval Office on Friday, Mr. Trump contradicted his top trade adviser in front of TV cameras about whether the agreement should be termed a “memorandum of understanding,” a phrase Mr. Trump said was not forceful enough.
Still, the president was upbeat. Mr. Trump in a tweet called the talks “very productive.”
The lack of detail about what the United States and China may agree to is prompting concern from both Republicans and Democrats, who worry that Mr. Trump may sign a deal that does little to change many of the practices that American companies say put them — and their workers — at a competitive disadvantage.
Lawmakers will get a chance to grill the administration about its plans this week when Robert Lighthizer, Mr. Trump’s top trade adviser, testifies about the China talks and other trade actions on Wednesday.
For now, Republicans are portraying the delay as a positive.
“Encouraging news from @POTUS that progress is being made in a trade deal with China,” Representative Patrick J. Toomey, a Republican from Pennsylvania, tweeted. “Hopefully this leads to an agreement that stops China’s theft of US intellectual property and avoids a full blown trade war.”
Complications could still arise, however, including China’s importance in helping the United States negotiate with North Korea. The Chinese have assisted the Trump administration in arranging another summit meeting with Kim Jong-un in Hanoi this week and Mr. Trump has often cited Mr. Xi’s relationship with Mr. Kim, which has put Mr. Trump in the awkward position of depending on China’s assistance while also trying to play tough and win a trade deal.