An internal US government document predicts 3,000 daily coronavirus deaths in the country by early June, according to The New York Times.
The document from the Trump administration appears to project that deaths will nearly double from the current level of about 1,750.
It seems to predict about 200,000 new coronavirus cases per day by the end of this month, up from about 25,000 currently.
The leaked document could throw into question the relaxation of social distancing measures across a number of states, as Donald Trump has pressed for economies to reopen and anti-lockdown protests were held over the weekend.
Health systems in some areas have struggled to cope with an influx of patients, and in some cases sufferers have been treated on stretchers in hospital corridors.
The Centers for Disease Control and Prevention has warned there “remains a large number of counties whose burden continues to grow”, although there has been some improvement in places such as New York City, New Orleans and Detroit.
So far, more than 67,000 people have died in the US and more than a million have been infected.
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As of last week, the University of Washington’s IHME predictive model projected a first wave of 72,400 coronavirus-related deaths.
On Sunday, Mr Trump said up to 100,000 people could die with coronavirus in the US – doubling the number he had forecast two weeks ago.
“We’re going to lose anywhere from 75, 80 to 100,000 people,” he told a virtual town hall on Fox News. “That’s a horrible thing. We shouldn’t lose one person over this.”
His figures are still less than what the government document predicts.
The Trump administration has responded to the New York Times report, denying the document’s authenticity.
The Johns Hopkins Bloomberg School of Public Health said: “These preliminary analyses were provided to FEMA to aid in scenario planning – not to be used as forecasts – and the version published is not a final version.
“These preliminary results are not forecasts, and it is not accurate to present them as forecasts.
“The information illustrates that there are some scenarios, including the premature relaxation of social distancing, that are likely to cause significant increases in the number of COVID-19 cases and deaths in the United States.”
White House spokesperson Judd Deere said: “This is not a White House document nor has it been presented to the Coronavirus taskforce or gone through inter-agency vetting.
“This data is not reflective of any of the modelling done by the taskforce or data that the task force has analysed.
“The president’s phased guidelines to open up America again are a scientific driven approach that the top health and infectious disease experts in the federal government agreed with.
“The health of the American people remains President Trump’s top priority and that will continue as we monitor the efforts by states to ease restrictions.”
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Officials said the projections assumed that states resumed normal activities immediately, not according to the phased guidelines unveiled last month.
Mr Trump has been accused of ignoring warnings about the risks of the virus in his daily briefings throughout January, and also has not yet joined a global pledge for research to find a vaccine.
World leaders, organisations and banks have pledged to give $8bn (£6.4bn).
Former foreign secretary David Miliband described the America’s absence from the global pledge as a “mystery”.
“At the moment, the US is not a good advertisement for the kind of global leadership or national reaction that would historically have been the case,” he said.
Mr Miliband continued: “Sadly so far the reaction to the crisis has been to compound the problem rather than to tackle it.
“Although it’s obviously right that every government has in the first instance to look after its own citizens, this disease shows that unless there is a global response then there won’t be a return to anything like economic or social normality.”