The US has become the first country in the world to record more than 2000 coronavirus deaths in a single day.
Figures from Johns Hopkins University show 2108 people died in the past 24 hours while there are now more than half a million confirmed infections.
The US could soon surpass Italy as the country with the most coronavirus deaths worldwide.
But experts on the White House Covid-19 task force say the outbreak is starting to level off across the US.
Dr Deborah Birx said there were good signs the outbreak was stabilising, but cautioned: "As encouraging as they are, we have not reached the peak."
President Donald Trump also said he expects the US to see a lower death toll than the initial predictions of 100,000 fatalities.
In other developments:
- Brazil became the first country in the southern hemisphere to surpass 1000 deaths with coronavirus
- The World Health Organization chief warned that lifting coronavirus lockdown measures too early could spark a "deadly resurgence" in infection
- Turkey ordered a 48-hour curfew in 31 cities - including Istanbul and Ankara - to start at midnight. The announcement, made just two hours before the curfew was due to start, sparked panic buying and crowds of shoppers
- Aid agencies expressed alarm after the first virus case was confirmed in Yemen, where years of civil war have devastated health systems
What are the latest US figures exactly?
The US now has at least 18,693 deaths and 500,399 confirmed cases, according to Johns Hopkins.
About half of the deaths were recorded in the New York area.
Italy has recorded 18,849 deaths while globally more than 100,000 people have died with the virus.
Researchers had predicted the US death toll would hit its peak on Friday and then gradually start to decline, falling to around 970 people a day by 1 May - the day members of the Trump administration have floated as a possible date to start reopening the economy.
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Why might the outbreak start levelling off soon?
Dr Anthony Fauci, US infectious diseases chief, concurred that the US was "starting to see the levelling off and coming down" of cases and deaths.
But he added that despite the "important advance", mitigation efforts such as social distancing should not be pulled back yet.
Dr Birx noted that the rate of increase appeared to be stabilising in hard-hit regions like New York, New Jersey and the city of Chicago.
She added that the US mortality rate was "significantly less than many of the other countries, when you correct them for our population".
But she emphasised the nation had yet to see the peak of the outbreak. "We need to continue to do what we did yesterday, and the week before, and the week before that because that's what, in the end, is going to take us up across the peak and down the other side."
On Friday, the governor of New York said the latest data showed the state was successfully "flattening the curve".
"Even though it's a grind, even though it's difficult, we have to stay with it," Governor Andrew Cuomo said, cautioning that it was still too early to relax social distancing measures.
The danger appears to be highest for America's minority communities, which have been disproportionately affected by Covid-19.
Dr Jerome Adams, the US surgeon general, said the trend was "alarming, but not surprising" given that minorities in the US generally had more chronic health conditions such as asthma, hypertension and diabetes.
"As a matter of fact, I have been carrying an inhaler in my pocket for 40 years out of fear of having a fatal asthma attack," continued Dr Adams, who is African-American.
In Friday's White House briefing, Trump said he had seen the drone images of coffins being stacked in a mass grave on New York's Hart Island.
Officials there say the island, which has been used to bury people with no next of kin for over 150 years, is now burying bodies at five times the normal rate.
Earlier in the day, Dr Fauci told CNN that officials are currently discussing whether to adopt immunity certificates for Americans who have safely survived the coronavirus and have antibodies in their blood to prove it.
The certificates might "have some merit under certain circumstances", he said, adding that antibody tests would be available next week.
Meanwhile, in Washington lawmakers are considering a "Covid-19 heroes fund" to provide direct payments to workers on the front line of the pandemic.
The Democratic-led proposal calls for a $13 hourly rate, on top of the pay that workers already receive from their employers. Payment would be capped at $25,000.
The money would go towards nurses, doctors, grocery store clerks, transit workers and other workers deemed essential.
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