“We are not opening all at once, but one careful step at a time,” Mr. Trump told reporters during a briefing at the White House.

Gov. Jay Inslee of Washington said he was pleased to see that the president’s guidelines were “hands off” and would not intrude on the rights of the states.

“The president recognized, finally, I think, that the rightful decision-making is with the states and the governors’ offices, both Republicans and Democrats,” Mr. Inslee said.

Mr. Trump essentially gave cover to mainly Republican governors of states in the South and West that have not been as hard hit by the pandemic to begin reopening sooner. The president, who has previously said that as many as 29 states could reopen soon, told governors on a conference call before his announcement that some of them were “in very, very good shape” and could move further and faster to resuming economic and social activities.

If they follow the guidelines, New York and other states in the Northeast, as well as states in the Midwest and West, that have seen large outbreaks would remain shuttered for weeks until new cases of the virus and death tolls fell and hospital capacity was restored.