WASHINGTON (REUTERS) - The United States Centres for Disease Control and Prevention (CDC) on Thursday (March 3) said some 93 per cent of the US population live in locations where Covid-19 levels are low enough that people do not need to wear masks indoors.

On Friday, the CDC dramatically eased its Covid-19 guidelines for when Americans should wear masks indoors, saying they could drop them in counties experiencing what it described as low or medium Covid-19 levels.

The latest figures are an increase from just a week ago, a further indication that Covid-19 hospitalisations - a key benchmark for the new masking recommendations - continue to fall.

When it announced the revised guidelines, the CDC said about 70 per cent of US counties and 72 per cent of the US population were in communities where indoor face coverings are no longer recommended. The CDC plans to update its county ratings weekly.

The agency said on Thursday that 85.4 per cent of counties now rank as low or medium risk and 92.9 per cent of the population lives in those counties.

Still to be determined is whether the Biden administration will extend mask requirements for transit hubs and on airplanes, trains and buses. The current transit mask order expires on March 18 but could be extended. The White House said this week that the issue is being evaluated.

The masking guidelines announced last week shifted from a focus on the rate of Covid-19 transmission to local hospitalisations, hospital capacity and infection rates.

Under the prior guidelines, 95 per cent of US counties were considered to be experiencing high transmission, leaving just 5 per cent of US counties under the agency's recommendation for abandoning indoor mask requirements.

A growing number of federal agencies have told government employees this week they can stop wearing masks indoors in federal buildings in the Washington, D.C. area and other low or medium Covid-19 areas, including the State Department, Pentagon, Transportation Department, Federal Aviation Administration and Justice Department.

The White House directed agencies to revise federal employee masking and testing rules no later than Friday, according to a memo on Monday first reported by Reuters. The guidance covers about 3.5 million employees at federal agencies.

In counties with low community Covid-19 levels, federal agencies also do not need to regularly screen unvaccinated employees for Covid-19, the guidance said.