Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases speaks as President Donald Trump listens during the daily briefing of the White House Coronavirus Task Force at the White House April 13, 2020 in Washington, DC.

White House health expert Dr. Anthony Fauci on Monday walked back his recent comments about the initial U.S. response to the coronavirus, saying he used "the wrong choice of words" a day earlier when describing "pushback about shutting things down."

Fauci's comments from a CNN interview Sunday – in which he said that more lives "obviously" could have been saved if the U.S. made earlier efforts to contain the virus – were seen by some as a critique of the Trump administration's handling of the crisis.

Trump later that evening retweeted a call to "#FireFauci." A White House spokesman said Monday that the president "is not firing Dr. Fauci," who "has been and remains a trusted adviser to President Trump."

Fauci on Monday evening defended his comments, and Trump's record on the coronavirus, while standing next to the president at the White House's daily briefing on the disease.

"I was asked a hypothetical question" about whether lives could have been saved if mitigation policies were put in place earlier, "and hypothetical questions sometimes can get you into some difficulty," Fauci said.

Fauci, the director of the National Institute of Allergy and Infectious Diseases, said that his response on CNN "was taken as a way that maybe somehow something was at fault here."

"I've been up here many times telling you mitigation works," Fauci said. "So if mitigation works and you initiate it earlier, you probably would have saved more lives. If you initiated it later, you probably would have lost more lives."

Fauci said that the "first and only time" that he and coronavirus response coordinator Dr. Deborah Birx talked to Trump about "shutdown"-like mitigation policies, "the president listened to the recommendation and went to the mitigation."

When Fauci and Birx went to Trump a second time advising him to extend the White House's social-distancing guidelines through the end of April, Trump "went with the health recommendations," Fauci said.

Asked about his comment from the interview that "there was a lot of pushback about shutting things down back then," Fauci said "that was the wrong choice of words."

"When people discuss [the mitigation policies], not necessarily in front of the president but when people discuss, they say, 'Well, you know, this is maybe going to have a harmful effect, on this or on that.' So it was a poor choice of words," he said.

"It wasn't anybody saying, 'No, you shouldn't do that,'" Fauci added.

Asked if he was clarifying his remarks "voluntarily," he replied: "Everything I do is voluntarily. Please. Don't even imply that."

After Fauci spoke, Trump returned to the lectern to walk through a timeline of the initial steps his administration took in January to prevent the disease from spreading to the U.S., all while bashing his critics in politics and the media.

Asked if he is on the same page with the doctor, Trump said, "We have been from the beginning."

He highlighted his decision on Jan. 31 to impose travel restrictions and quarantine rules aimed at people coming from China, when there were just a handful of Covid-19 cases in the U.S.

Reporters at the coronavirus briefing were then shown a campaign-style video touting Trump's performance in response to the crisis. The video – complete with inspiring music, visual filters and text graphics such as "President Trump took decisive action" – offered a pointed example of Trump using the daily briefings to tout his own successes, rather than merely provide updates on the disease.

Critics have accused the president of abusing the briefings, which are carried on most major networks, by treating them as de facto campaign rallies, which have been canceled amid the pandemic.