His move came as additional governors took action to stop the spread of the virus. With new orders on Monday from the governors of Arizona, Maryland and Virginia, as well as the mayor of the District of Columbia, more than half of the 50 states and three out of four Americans are or will soon be under the directive to remain at home.

They took that action as the number of cases in New York climbed past 66,500 and the number of deaths surpassed 1,200, by far the most of any state. Layoffs continued apace, with Macy’s announcing it would furlough a “majority” of its 125,000 workers. Gap said it would do the same for 80,000 store employees in the United States and Canada.

In the past two days, Mr. Trump has dispensed with the assertion that the cure could be worse than the disease and circled back closer to the tenor of the warnings he has gotten from health advisers. Rather than lift the restrictions he had outlined by April 12, he extended them to April 30 and said on Monday that they “may be even toughened up a little bit,” although a national stay-at-home order like those in New York and California was “pretty unlikely, I would think, at this time.”

At Monday’s briefing, Mr. Trump recycled his line from a couple of weeks ago putting the virus ahead of the economy among his concerns. “The economy is No. 2 on my list,” he said. “First, I want to save a lot of lives.”

Indeed, he again accentuated the starkest projections given to him by public health officials, noting that more than two million Americans could have died in the absence of any measure, perhaps to set expectations so that any eventual death toll below that can be cast as a victory.