NEW YORK — U.S. movie theaters have closed nationwide due to the coronavirus pandemic, turning dark nearly all of the country’s 40,000-plus screens in an unprecedented shutdown.

With most of Hollywood’s March and April releases already postponed, the Walt Disney Co. on Tuesday also cleared out its May releases as well, including Marvel’s “Black Widow.”

The largest chains had tried to remain open even as Hollywood postponed its upcoming release plans and guidelines for social distancing steadily diminished the recommended size of crowds. But after President Donald Trump on Monday urged against gatherings of more than 10 people, AMC Theaters, the nation’s largest chain, said Tuesday its theaters would close altogether.

AMC said the latest guidelines made movie theater operations “essentially impossible.” It said it would close all locations in the U.S. for at least six to 12 weeks. Regal, the second largest chain, said Monday that its theaters would close until further notice.

The Walt Disney Co. also indefinitely postponed “Black Widow,” which had been set to open May 1. Marvel movies have for years been the regular kickoff to the summer movie going season. The company also put off the releases of “David Copperfield (May 8) and “The Woman in the Window” (May 15).

With movie theaters locked down for the foreseeable future, some studios took the extraordinary step of funneling new or recently released films onto home viewing platforms. Universal Pictures said Monday it will make its current and upcoming films available for on-demand rental, becoming the first major studio to break the traditional theatrical window of 90 days due to the pandemic.

The studio said it will put movies currently in theaters — “Invisible Man,” “The Hunt,” “Emma”– up for rental as early as Friday. It also said that “Trolls World Tour,” one of the only major releases left on the April calendar, will debut in theaters and on-demand services simultaneously. A 48-hour rental will cost $19.99.

Most of Europe’s cinemas have already shut down, as have those in China, India and elsewhere. North America’s shutdown came gradually. On Sunday, the mayors of New York and Los Angeles ordered their cities’ theaters closed. Governments in Massachusetts and Quebec also closed theaters.

Cinemark, the nation’s third-largest chain, also announced its theaters would shutter Wednesday. Chains including the Alamo Drafthouse, Landmark Theatres, Showcase Cinemas and Bow Tie Cinemas have closed.

New York’s Film Forum marquee, usually adorned with titles, instead bore a paraphrased Franklin Roosevelt quotation: “We have nothing to fear but fear itself.”

The Alamo Drafthouse put an “Intermission” card up on its website.

“This news – this situation – is devastating,” the 41-theater circuit based in Austin, Texas, wrote.