Walmart says shoppers must wear masks inside its stores starting Monday — the largest retailer to join a growling list of companies making face covering mandatory across the nation.

Walmart and Sam's Club are joining Costco, Starbucks, Best Buy and others in implementing a nationwide requirement for customers to wear masks inside their stores. Walmart said it's creating a new job of "health ambassador," who will be specially trained to "work with customers who show up at a store without a face covering to try and find a solution."

The National Retail Federation says it hopes Walmart's move is "a tipping point in this public health debate" and urged all retailers to adopt a similar policy.

"Shopping in a store is a privilege, not a right," the trade group said in a statement on Wednesday. "If a customer refuses to adhere to store policies, they are putting employees and other customers at undue risk."

Walmart, in a blog post on Wednesday, cited new spikes in coronavirus cases across the U.S. — four months since the World Health Organization declared a pandemic. The company says some 65% of store locations are already in areas with "some form of government mandate on face coverings."

Many retailers have long hesitated to require masks inside stores for fear of upsetting some customers and putting their workers in danger by turning them into enforcers of the policy. Business groups, including the U.S. Chamber of Commerce, wrote to the White House this month, asking for a national mask standard.

"We know this is a simple step everyone can take for their safety and the safety of others in our facilities," Walmart officials wrote on Wednesday, adding:

"We know some people have differing opinions on this topic. We also recognize the role we can play to help protect the health and well-being of the communities we serve by following the evolving guidance of health officials like the CDC."

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