The United States was slow in recognizing that the novel coronavirus threat in the country was from Europe, Robert Redfield, director of the US Centers for Disease Control and Prevention, or CDC, admitted for the first time on Tuesday.

"The introduction from Europe happened before we realized what was happening," Redfield said in an interview with ABC News.

"By the time we realized the Europe threat and shut down travel to Europe, there was probably already two or three weeks of 60,000 people coming back every day from Europe," he added.

"That's where the large seeding came in the Unites States."

The US restricted travel from China on Feb 2 and from Europe on March 13, but by March 8, COVID-19 was already circulating among the community in New York City and, by March 15, community transmission of the virus was already widespread, a recent analysis from the CDC found.

By the time the Trump administration banned travelers from Europe, the virus was already spreading in New York City, according to the report.

Testing was also limited at the start of the epidemic there, allowing people with undetected infection to spread the virus.

Redfield also admitted that there have been problems with the federal response. "Yes, there's been mistakes," he said. "And, yes, we fail. We're in it doing the best we can and we're trying to make the best judgments we can."

On Tuesday, a half-dozen US states in the South and West reported one-day records for COVID-19 deaths, and cases in Texas passed the 400,000 mark. More than 1,300 lives were lost in the US nationwide on Tuesday, the biggest one-day increase since May, according to Reuters.

The US had reported 4,352,084 confirmed cases as of Tuesday, with its death toll at 149,258, according to the Johns Hopkins University.

Approval rating

US President Donald Trump on Tuesday said during a news conference at the White House that he's wondering why Anthony Fauci, a top infectious diseases expert and key member of the White House coronavirus task force, has enjoyed a higher approval rating among the public than he has on the handling of the coronavirus pandemic.

"He's got this high approval rating, so why don't I have a high approval rating with respect－and the administration, with respect to the virus?" Trump asked.

"It's interesting: He's got a very good approval rating, and I like that. It's good. Because remember, he's working for this administration," the president continued.

"We could have gotten other people. We could have gotten somebody else. It didn't have to be Dr Fauci."

Polls have shown Fauci, a career health official who has served as director of the US National Institute of Allergy and Infectious Diseases since 1984, to be among the most trusted voices in the country on the pandemic since it started months ago.

Nearly two-thirds of US voters say they trust the information Fauci is providing about the coronavirus, while 67 percent say they do not trust the information Trump is giving, according to a Quinnipiac University poll released on July 15.

Trump also renewed his defense of using anti-malaria drug hydroxychloroquine against COVID-19 on Tuesday, despite medical evidence disproving its effectiveness.

"It's safe. It doesn't cause problems. I had no problem. I had absolutely no problem," Trump said during a news briefing at the White House.

"It didn't get me, and it's not going to, hopefully, hurt anybody."

The president was referencing his own use of hydroxychloroquine earlier this year.

"I took it for a 14-day period," he said. "Many doctors think it's extremely good, and some people don't ... I think it's become very political."

Fauci warned early on Tuesday against using hydroxychloroquine as a coronavirus treatment.

"The overwhelming prevailing clinical trials that have looked at the efficacy of hydroxychloroquine have indicated that it is not effective in coronavirus disease," Fauci said on ABC's Good Morning America.

Hydroxychloroquine is used to treat malaria and rheumatoid conditions such as arthritis, according to the National Institutes of Health.

"In various studies, the drug had demonstrated antiviral activity, an ability to modify the activity of the immune system, and it has an established safety profile at appropriate doses, leading to the hypothesis that it may have also been useful in the treatment of COVID-19," the agency explained.