White House coronavirus response coordinator Dr. Deborah Birx told Fox News in an interview on Sunday that there is "clear scientific evidence" that masks work.
Pressed on whether President Donald Trump should wear one, she added that she assumes Trump is able to keep six feet of distance "in a majority of cases".
"What we have said to people is there is clear scientific evidence now, by all the droplet experiments that happened, and that others have done, to show that a mask does prevent droplets from reaching others," Birx said when asked what she would tell people who say they have a right not to wear a mask in public.
"Out of respect for each other, as Americans that care for each other, we need to be wearing masks in public when we cannot social distance," she added.
Birx was then asked whether she wished Trump wore a mask in public, both from a messaging perspective and for safety reasons.
"Well the President did wear a mask while he was less than six feet in an occasion where that was important -- I think when he was traveling last week," Birx said, adding, "I'm not with him every day and every moment, so I don't know if he can maintain social distance."
"I've asked everybody independently to really make sure that you're wearing a mask if you can't maintain the six feet. I'm assuming that in a majority of cases, he's able to maintain that six feet distance."
The comments from Birx come several days after Trump refused to wear a mask in front of cameras while visiting a Ford plant in Michigan.
As he walked through the facility -- where Ford rules say everyone must wear a mask -- he was surrounded by company executives whose faces were covered.
In a separate interview with ABC, Birx commented on large crowds seen at beaches on Saturday that appeared not to be social distancing, stressing that "there's asymptomatic spread. And that means that people are spreading the virus unknowingly."
"And this is unusual in the case of respiratory diseases in many cases. So, you don't know who's infected. And so we really want to be clear all the time that social distancing is absolutely critical. And if you can't social distance and you're outside, you must wear a mask. These are items that really critical to protect individuals," she said.
Birx also left open the possibility of recommending the nation shut down again if there is another major outbreak, saying "it's difficult to tell" if she could see the country shuttering again.