The Pentagon announced on Wednesday that "masks are no longer required indoors" at the building.
The decision was made per new guidelines from the Centers for Disease Control and Prevention (CDC), according to a press release, Xinhua news agency reported.
"Individuals may wear a mask if they choose regardless of Covid-19 community level," the release added.
The Pentagon also lowered its health protection level in the building to "Bravo", allowing up to 50 per cent occupancy there as well as "more options for seating in the food court".
The CDC last week eased its mask recommendation for most Americans.
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The White House outlined a new strategy for the next phase of handling the Covid-19 pandemic on Wednesday.
The 96-page plan focuses on, among other things, protecting against and treating the disease, and preparing for new variants.
"We've reached a new moment in the fight against Covid-19 where severe cases are down to a level not seen since July of last year," US President Joe Biden said in his State of the Union address on Tuesday night.
"I can't promise a new variant won't come," he warned. "But I can promise you we'll do everything within our power to be ready if it does."
The US has reported more than 79 million Covid-19 cases and 953,000 deaths, both the highest in the world, according to Johns Hopkins University data.
Steven Thrasher, a Scientific American columnist and professor at Northwestern University, wrote in February that "mass media and policy makers are pushing for a return to pre-Covid times while trying to normalize a staggering death toll".
