WASHINGTON — The Trump administration is formalizing new guidance to recommend that many Americans wear face coverings in an effort to slow the spread of the new coronavirus, as the president is aggressively defending his response to the public health crisis.

The recommendations, still being finalized Thursday, were expected to apply to those who live in areas hard-hit by community transmission of the virus that causes COVID-19. A person familiar with the White House coronavirus task force’s discussion said officials would suggest that non-medical masks, T-shirts or bandannas be used to cover the nose and mouth when outside the home — for instance, at the grocery store or pharmacy. Medical-grade masks, particularly short-in-supply N95 masks, would be reserved for those dealing directly with the sick.

The person spoke on condition of anonymity to discuss the proposed guidance before its public release.

President Donald Trump, who was tested again for coronavirus Thursday using a new rapid test, indicated he would support such a recommendation. “If people wanted to wear them, they can,” he said.

“It’s not a bad idea, at least for a period of time,” Trump had said earlier in the week.

The White House said Trump’s latest test returned a negative result in 15 minutes, and said Trump was “healthy and without symptoms.”

Dr. Deborah Birx, the task force’s coordinator, told reporters the White House was concerned that the mask guidance would lead to a “false sense of security” for Americans. She said new data show that the administration’s social-distancing guidelines were not being followed to the extent necessary to keep virus-related deaths to a minimum.

In response to recent studies, the CDC on Wednesday changed how it was defining the risk of infection for Americans. It essentially says anyone may be a considered a carrier, whether they have symptoms or not.

The virus spreads mostly through droplets from coughs or sneezes, though experts stress that the germ is still not fully understood.