President Donald Trump has warned that the US pandemic will probably "get worse before it gets better", as he revived his coronavirus briefings.
Mr Trump also asked all Americans to wear face coverings, saying "they'll have an effect" and show "patriotism".
He was not wearing a mask at the briefing, but has previously downplayed such personal protective equipment.
The president's aides have reportedly asked him to adopt a new tone as virus caseloads spike across the US.
The daily White House news conferences ended soon after Mr Trump suggested in April during freewheeling remarks from the podium that the virus might be treated by injecting bleach into people.
In his first White House coronavirus briefing for months on Tuesday, a more scripted president echoed what public health officials on his pandemic task force have been saying. as he warned: "It will probably unfortunately get worse before it gets better."
He added: "We're asking everybody that when you are not able to socially distance, wear a mask, get a mask.
"Whether you like the mask or not, they have an impact, they'll have an effect and we need everything we can get."
Mr Trump has been reluctant to wear a mask himself in front of the media, donning one for the first time recently during a visit to a military hospital.
The president continued: "We're asking Americans to use masks, socially distance and employ vigorous hygiene - wash your hands every chance you get, while sheltering high risk populations.
"We are imploring young Americans to avoid packed bars and other crowded indoor gatherings. Be safe and be smart."