His comments came after the country's top infectious disease expert, Dr Anthony Fauci, urged state and local leaders to be "as forceful as possible" in getting people to wear masks.
Wearing face coverings, Dr Fauci added, is "really important" and "we should be using them, everyone".
The wearing of face coverings has become highly politicised in the US.
The majority of state governors have now ordered that the wearing of masks outdoors be mandatory, rather than a personal choice. Among them are Republican governors, including Kay Ivey of Alabama, who have reversed their initial opposition to the mandates.