As a practical matter, the stay-at-home orders that have kept much of the nation hunkered down have been made by governors and mayors. But many were moved to act in part by the federal guidelines meant to slow the spread of the coronavirus.

Mr. Trump, who has often sounded impatient for the nation — and particularly its economy — to reopen, said that he would listen to the advice of the medical experts before acting. But he also said that he would convene a new task force with business leaders on it next week to think about when to act.

At a news briefing at the White House on Friday, Dr. Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases, said he assumed that any lifting of restrictions would cause an increase in cases, heightening the need to be able to identify, isolate and trace them.

And in an interview on CNN on Friday, Christopher Murray, the director of the Institute of Health Metrics and Evaluation at the University of Washington, which had created a model for Covid-19 deaths, said the data he had seen had persuaded him that a premature lifting of social distancing restrictions — without adequate testing and contact tracing, among other safeguards — could see a renewed surge in infections, and deaths.

“It’s enough to say that if we were to stop at the national level May 1, we’re seeing a return to almost where we are now sometime in July,” Dr. Murray said.