Centers for Disease Control and Prevention (CDC) on Friday revised its guidance for Americans on wearing masks to protect against COVID-19, recommending donning "the most protective mask you can" while stopping short of advocating nationwide usage of N95 respirators.

In another step, the White House on Friday said the government will begin shipping 500 million COVID-19 tests to Americans later this month without charge.

The CDC said it wants to encourage Americans to wear masks rather than push them to wear the highest-grade face protection, but also explicitly said that respirators provide the best level of protection.

The CDC last May announced that fully vaccinated people could shed their face coverings, as COVID-19 cases were then on the decline.

But in July, the CDC said fully vaccinated people should wear masks in indoor public places in regions where COVID-19 was spreading rapidly.

Biden, a Democrat, this week again urged people to wear masks and noted that about a third of Americans report they do not wear a mask at all.

Many Republican-leaning states have no mask requirements.