July 15 (Reuters) — Shoppers at Walmart Inc. stores will have to wear face coverings, the world's largest retailer said on Wednesday, mandating what is widely seen as an effective measure to control the spread of the new coronavirus.

As coronavirus infections spike in many states across the country, face masks have become the leading recommendation from health experts and government officials looking to control the pandemic, while reopening the economy.

Walmart said about 65% of its over 5,000 U.S. stores, including its wholesale Sam's Club outlets, are located in areas where there is already some form of government mandate on face coverings. Its new policy will now apply to all stores starting Monday.

Trade group National Retail Federation on Wednesday pushed for retailers to adopt a nationwide policy that requires customers to wear masks, and hoped Walmart's decision would galvanize other companies to take similar action.

Best Buy Co. Inc. and Starbucks Corp have already mandated face masks at their U.S. outlets.

While many retailers have recommended masks for months, they were hesitant to make it a requirement, for fear of antagonizing shoppers, with numerous videos posted online on confrontations between customers and employees.

But with more than 136,000 COVID-19 related deaths in the United States and some states at risk of going back into lockdown, the ground has shifted.

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

Walmart said employees stationed at the entrance of its own and Sam's Club stores will remind customers of its new policy.

(Reporting by Uday Sampath in Bengaluru; Editing by Shinjini Ganguli)