He suggested that not enough Americans are adhering to social distancing or wearing face coverings. “Clearly we are not in control right now,” he said.
During the conference, he said about half of all new infections are located in four states.
Earlier, New York Governor Andrew Cuomo, said almost half of all US citizens must self-quarantine if they travel to New York.
On Tuesday, the US’ case number went up by over 40,000 in one day for the fourth time in the past five days.
The hike in coronavirus cases is happening especially in southern and western states.
The new surge has caused at least 16 states to halt their lockdown easing or reinstate the lockdown restrictions they previously had in place, according to CNN.
Dr Fauci said Florida, Arizona, Texas and California are the four states currently being affected the most by the pandemic.
In some states, the new restrictions being applied come over a month after they started lifting their lockdowns.
On Tuesday, Governor Cuomo added more people to the list of travellers who must self-quarantine for 14 days if they enter the state. Currently, 16 states are listed.
READ MORE: Trump embarrassment as Republican Party split on face masks
The recently included states are California, Georgia, Iowa, Idaho, Louisiana, Mississippi, Nevada and Tennessee.
Alabama, Arkansas, Arizona, Florida, North Carolina, South Carolina, Texas and Utah were on the list before too.
The current decree requires that 48 percent of all Americans self-quarantine upon arrival to New York, according to a USA Today study.
A Senate board heard the director of the National Institute of Allergy and Infectious Diseases testify on the reopening of schools and businesses.
Coronavirus: China becomes first to use experimental vaccine [REVEALED]Piers Morgan confronts Donald Trump on ‘white power’ tweet [INSIGHT]Trump humiliation as US president shuts down Russian bounty claims [UPDATES]
He said states were “skipping over” standards that should be met prior to reopening, adding that infections will subsequently surge.
“I can’t make an accurate prediction, but it is going to be very disturbing, I will guarantee you that,” he told Senator Elizabeth Warren.
“Because when you have an outbreak in one part of the country even though in other parts of the country they’re doing well, they are vulnerable.”
“We can’t just focus on those areas that are having the surge. It puts the entire country at risk.”
Robert Redfield, the director of the Centers for Disease Control and Prevention (CDC) – who was also present on Tuesday – said that 12 states have seen hospitalisations hike, and Arizona has reported an increasing death toll.