The United States now has more confirmed Covid-19 cases than any other country.
With more than 85,500 positive tests, it has overtaken China (81,782 cases) and Italy (80,589).
The U.S. death toll at almost 1,300 Covid-19-related fatalities lags behind China (3,291) and Italy (8,215).
President Donald Trump said it was "a tribute to the amount of testing that we're doing", when asked about the latest figures at a White House briefing on Thursday, March 26 afternoon.
Vice-President Mike Pence said coronavirus tests were now available in all 50 states and more than 552,000 tests had been conducted nationwide.
Trump also expressed doubt about the official numbers coming out of China.
He told reporters: "You don't know what the numbers are in China."
New research on Thursday estimated Covid-19-related deaths in the U.S. could hit 80,000 over the next four months, even if people observe strict social distancing.
As many as 2,300 patients could die each day by April, according to the study from the Institute for Health Metrics and Evaluation at the University of Washington's School of Medicine.
Trump has been criticised for setting the goal of reopening the country by Easter Sunday, April 12.
It has emerged that an unprecedented 3.3 million Americans have been laid off because of the virus.
The grim milestone came as Trump predicted the nation would get back to work "pretty quickly".