WASHINGTON - Anthony Fauci, the government's top infectious-disease specialist, warned Tuesday that the United States could soon have 100,000 new coronavirus cases a day "if this does not turn around"- a surge that would be more than twice as many as the record so far and three times as many as the original peak this spring. 

Fauci said that recent images of Americans gathering in bars or other crowds foreshadow a greater spike in infections that "is going to be very disturbing ... We're going to continue to be in a lot of trouble, and there's going to be a lot of hurt if that does not go away."

Fauci gave his bleak assessment in response to questions during his latest appearance on Capitol Hill to brief lawmakers on the state of the pandemic as new infections are rampant across much of the South and West, with hospitalizations escalating in a dozen states.

He and other top health officials acknowledge that the nation's public health system was ill prepared for a major infectious-disease outbreak, as the Republican chairman of the Senate Health, Education, Labor and Pensions Committee called on President Donald Trump to start heeding federal guidance to wear a mask in public.

"Unfortunately, this simple lifesaving practice has become part of the political debate that says this: If you're for Trump, you don't wear a mask. If you're against Trump, you do," said the chairman, Sen. Lamar Alexander of Tennessee. "That's why I've suggested that the president occasionally wear a mask, even though in most case it's not necessary for him to do so. The president has plenty of admirers. They would follow his lead."

The rare rebuke from a senator of the president's own political party attests to a disturbing reality for GOP politicians that the pandemic has veered lately from primarily Democratic-leaning states to red parts of the United States.

The hearing took place as Republican governors of newly hard hit states, including Texas and Florida, have been rescinding reopening plans in the face of surging cases of the virus that has killed at least 124,000 people in the U.S. since February.

Last weekend, the U.S. had a record daily number of confirmed new cases - 44,792. That is 30 percent higher than 34,203 on April 25, the peak day in the original surge of covid cases this spring.

At Tuesday's hearing, Fauci, director of the National Institutes of Health's National Institutes of Allergy and Infectious Diseases, initially declined to directly answer a question by Sen. Elizabeth Warren, D-Mass., about how many deaths and infections Americans should expect before the pandemic ends.

"It's going to be very disturbing," Fauci replied. "I will guarantee you that, 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 ... It puts the entire country at risk." Then Fauci added, "I would not be surprised if we go up to 100,000 a day if this does not turn around, and so I am very concerned."

He also told senators that federal and state guidance this spring for people to stay at home to avoid exposure to the virus led about half the United States to shut down - far less compliance than in many European countries, he said, where 95 percent of activities in those nations shut down. As a result, he said, the slowdown of the virus's spread among Americans has been less pronounced.

On another aspect of the nation's response to the pandemic, Robert Redfield, director of the Centers for Disease Control and Prevention, acknowledged the ability to trace the contacts of people infected by the coronavirus has been hampered by outdated public health data systems.

In response to questions from Sen. Lisa Murkowski, R-Alaska, Redfield said, that records of people possibly exposed to the virus "really are in need of aggressive modernization ... There are a number of counties still doing this pen and pencil."

Contact tracing - finding the people with whom an infected person has been in proximity - is regarded by public health specialists as a crucial tool in trying to contain an infectious virus, along with testing and isolating the people who have been exposed.

And Sen. Amy Baldwin, D-Wis., asked Redfield whether the Trump administration would consider moving from recommendations to businesses about how to reopen safely to compulsory standards by the Labor Department's Occupational Safety and Health Administration.

Baldwin noted that some companies are following federal guidance, but others are not. She singled out American Airlines for returning to its practice of trying to fill every seat on planes, rather than leaving a distance between passengers.

Redfield replied that Labor Secretary Eugene Scalia is a member of the White House's coronavirus task force, but said, "that specific topic we have not had directly."

Also at the hearing, Brett Giroir, an assistant secretary at the Department of Health and Human Services who coordinates coronavirus testing, said that as far as he knows, he remains the U.S. representative to the World Health Organization. Trump said a month ago that the United States "will today be terminating our relationship" with the WHO.

Giroir told senators he was confirmed as a WHO representative in early May. "I have not been recalled," he said. "I have not been given direction to recall myself."