The United States could see 100,000 new coronavirus cases a day, top US infectious disease expert Anthony Fauci warned Tuesday.

"We are now having 40-plus thousand new cases a day," Fauci said in testimony to the Senate health and education committee.

"I would not be surprised if we go up to 100,000 a day if this does not turn around," Fauci said. "And so I'm very concerned."

The director of the National Institute for Allergy and Infectious Diseases declined to predict a figure for the expected number of deaths in the United States from the pandemic but said it is going to be "disturbing."

There have been at least 126,000 deaths from COVID-19 in the United States so far.

Four US states -- Arizona, California, Florida and Texas -- are accounting for about half of the new cases.