President Biden is said to be giving "strong consideration" to new requirements for federal employees to help arrest the spread of the delta variant of the coronavirus.
Under the policy, federal employees who are not confirmed as vaccinated would be required to wear masks at all times while at work and be tested regularly for the virus, the source said, speaking on the condition of anonymity.
In a statement, Biden said he would lay out his next steps on how to get more Americans vaccinated on Thursday, noting that vaccinations are the best way to protect against the delta variant.
"More vaccinations and mask wearing in the areas most impacted by the Delta variant will enable us to avoid the kind of lockdowns, shutdowns, school closures, and disruptions we faced in 2020," he said.
But Walensky said the agency had to take into account the surge in cases, and data that shows that while rare, vaccinated people can still contract and spread the virus.
"The delta variant is showing every day its willingness to outsmart us," she said.