The US surgeon general has warned of the worsening fallout from coronavirus, saying: "This is going to be the hardest and the saddest week of most Americans' lives."
The number of people infected in the US has exceeded 300,000, with the death toll climbing past 8,400.
More than 3,500 of those deaths are in New York state.
Much of the country is under orders to stay home, and federal officials said they had seen signs that people were listening to the message about social distancing.
But the Trump administration is also emphasising that the worst is yet to come for many communities.
"This is going to be our Pearl Harbour moment, our 9/11 moment, only it's not going to be localised," said surgeon general Jerome Adams.
"It's going to be happening all over the country. And I want America to understand that."
Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said the coming week was "going to be shocking to some".
"But that's what is going to happen before it turns around, so just buckle down," Dr Fauci said. He added that the rate of new cases would determine whether the US was putting the worst behind it.
"We've seen that in Italy," Dr Fauci said. "We're going to hopefully be seeing that in New York very soon and that's the first sign of that plateau and coming down."
Dr Fauci also warned that unless the world gets the virus under control, it would "assume a seasonal nature".
"We need to be prepared that, since it unlikely will be completely eradicated from the planet, that as we get into next season, we may see the beginning of a resurgence," Dr Fauci said.
"That's the reason why we're pushing so hard in getting our preparedness much better than it was."