Walmart Inc. will require customers to wear masks in all of its U.S. stores to protect against the coronavirus, an admission that the nation’s pandemic has reached new heights and setting up potential confrontations with customers who refuse to don them.

The measure will go into effect starting July 20, U.S. Chief Operating Officer Dacona Smith said in a blog post Wednesday. The retailer will place employees, dubbed “Health Ambassadors,” near the entrance to “remind those without a mask of the new requirements,” it said. Stores will have a single entrance.

“While we’re certainly not the first business to require face coverings, we know this is a simple step everyone can take for their safety and the safety of others in our facilities,” Smith said in the announcement. The requirement also applies to Sam’s Club, Walmart’s membership-based warehouse retail division.

Walmart’s decision follows similar moves by Costco Wholesale Corp., Starbucks Corp. and Best Buy Co. Walmart already demands that its workers wear masks and shoppers had been encouraged to do so with signage.

Most major retailers and drugstore chains require masks in places where state or local governments say they are mandatory, and about two-thirds of Walmart’s stores are located in areas with some mask mandate. But few have made it a nationwide policy, perhaps fearful of wading into what’s become a bitter political issue that has led to violent, even fatal, confrontations between retail workers and customers who refuse to cover their face.

As the pandemic worsens, though, and the number of new cases hits fresh highs in several states, some executives have changed their thinking. In an interview with Bloomberg Television Monday, Walmart Chief Executive Officer Doug McMillon said requiring masks nationwide was on his mind.

‘Differing Opinions’

Still, getting every customer to wear a mask is much easier said than done.

Best Buy, the consumer electronics retailer, said Tuesday that small children and those unable to wear a mask “for health reasons” can still enter without one. The concession to those with health concerns raises one of the thornier problems with mask mandates: customers who simply don’t want to wear one for whatever reason can just claim to have a health problem, and store employees are unable to demand proof of their specific condition due to privacy concerns.

“We know it may not be possible for everyone to wear a face covering,” Walmart’s Smith said in the announcement. “We know some people have differing opinions on this topic. Our associates will be trained on those exceptions to help reduce friction for the shopper and make the process as easy as possible for everyone.”

Worker advocates say the process is anything but easy. The United Food and Commercial Workers International Union, which represents more than a million employees in supermarkets and food-processing plants, said June 25 that 82 grocery workers it represents have died from Covid-19, the disease caused by the virus, and 11,507 workers have been impacted in some way, usually by being exposed to the virus.

“This pandemic is real, and the risks to frontline workers are growing,” UFCW International President Marc Perrone said in a recent call with reporters. On the call, a worker at a Kroger Co. supermarket said she stopped asking customers to wear masks after a shopper said, “I don’t give a damn about your health.”