Another letter sent last week by 57 House Democrats led by Representative Andy Levin of Michigan made similar points: “During World War II, our country adapted to the demands of the time to produce mass quantities of bombers, tanks, and many smaller items needed to save democracy and freedom in the world. We know what the demands of this time are, and we must act now to meet these demands.”

Senator Jack Reed, Democrat of Rhode Island, said that Defense Secretary Mark T. Esper told him on Tuesday that the Pentagon would provide federal health workers with five million respirator masks and 2,000 specialized ventilators. “The American public is on wartime footing in terms of battling the spread of this disease, and the Pentagon has to be part of the effort to help protect the health and safety of the American people,” Mr. Reed said.

But Mr. Trump said on Tuesday that he was not ready to invoke the Defense Production Act. “We’re able to do that if we have to,” he told reporters. “Right now, we haven’t had to, but it’s certainly ready. If I want it, we can do it very quickly. We’ve studied it very closely over two weeks ago, actually. We’ll make that decision pretty quickly if we need it. We hope we don’t need it. It’s a big step.”

Passed in 1950 shortly after American troops went to war defending South Korea against an invasion from North Korea, the Defense Production Act was based on powers used during World War II and authorized the president to require businesses to prioritize and accept contracts necessary for national defense.

Over the years, its scope has been expanded to include domestic preparedness and national emergencies. A president can make direct loans or loan guarantees and purchase commitments, subsidies or other incentives to influence industry to help in times of crisis.

Other key decisions outlined as options for the president include distributing medical supplies and equipment from the Strategic National Stockpile, providing money to states to help them meet demands caused by the coronavirus outbreak and prioritizing the distribution of essential resources to focus on areas most in need.

“The spread and severity of Covid-19 will be difficult to forecast and characterize,” the government plan said. It warned of “significant shortages for government, private sector, and individual U.S. consumers.”