ABC News March 15, 2021

Biden, Fauci appear at odds over calling on Trump to urge supporters get vaccinated

WATCH: Why are people hesitant to trust a COVID-19 vaccine?

President Joe Biden appeared to be at odds with his top scientist in the pandemic fight, Dr. Anthony Fauci, about whether former president Donald Trump should urge his supporters to get vaccinated, given a poll that shows they are the Americans most likely not to get the shots.

"Should President Trump help promote the vaccine amongst skeptics, sir? Especially those Republicans who say that they’re not willing ... ," a reporter at the White House asked Biden at the end of an event Monday.

"I'm hearing a lot of reports from serious reporters like you saying that. I discussed it with my team, and they say the thing that has more impact than anything Trump would say to the MAGA folks, is what the local doctors, what the local preachers, what the local people in the community say," he responded. "So, I urge all local [doctors] and ministers and priests to talk about why it's important to get that vaccine, and even after that, until everyone is, in fact, vaccinated to wear this mask."

Jonathan Ernst/Reuters
National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci addresses reporters at the White House on Jan. 21, 2021.

A day earlier, Fauci said he wishes Trump would use his influence over supporters to encourage them to get the vaccine, saying it would "be a game changer" during an appearance on Fox News Sunday.

"It seems like an intrinsic contradiction, the fact that you had a program that was started during his presidency and he's not out telling people to get vaccinated. I wish he would. He has such an incredible influence over people in the Republican Party,” Fauci said. "It would really be a game changer if he did."

MORE: 69% of Americans say they've gotten or plan to get COVID-19 vaccine: Poll

While 30% of Americans said they would not get the vaccine if it became available to them, the percentage was far greater among white men, and those who voted for Trump are the most likely not to get the vaccine, according to a recent NPR/PBS NewsHour/Marist poll. Forty-nine percent of white men said they would not get vaccinated if it was available to them, and 47% of those who supported Trump in 2020 reported they would get the vaccine.

Trump and former first lady Melania Trump both received their vaccines before his term ended, but he made no public statement at the time, reports surfacing only after he left office. A Trump spokesperson did not respond to an ABC News request for comment Monday.

When pressed about what the Biden White House was doing to reach out to Americans across the aisle, Psaki on Monday stressed that his goal is to vaccinate all Americans "not just those who voted for him." Psaki touted the efforts by the administration to partner with local health care providers and she even previewed an event Tuesday in which Fauci will meet with evangelical leaders.

Patrick T. Fallon/AFP via Getty Images
A nurse administers a dose of the Moderna Covid-19 vaccine at a clinic for Catholic school education workers including elementary school teachers and staff at a vaccination site at Loyola Marymount University, March 8, 2021, in Los Angeles.

"One of the steps we've taken, and we can effectively do outside of any partisan politics is ensure that there are locations with trusted, interested locations, community health centers, pharmacies, where anybody of any political persuasion can get the vaccine, and they don't need to wear a Joe Biden sticker in order to do that," Psaki said.

But at a briefing on Friday, Psaki noted the limitations of Biden's messaging given the partisan divide.

“We recognize as a Democratic administration with a Democratic president that we may not be the most effective messenger to communicate with hard core supporters of the former president, and we have to be clear eyed about that," Psaki said.

MORE: Dr. Fauci reflects on the pandemic's 1-year mark and how to get back to 'normality'

Psaki also addressed ads released last week featured every living president, including former Republican President George W. Bush, in public service announcements encouraging Americans to get vaccinated.

The Ad Council, which was behind the ads, told ABC News that the ads were filmed at the inauguration of Biden in January, which Trump did not attend.

MORE: Former presidents, except Trump, urge Americans to be vaccinated in new PSA

"Every other living former president ... has participated in public campaigns, they did not need an engraved invitation to do so. So, he may decide he should do that. If so, great," Psaki said. "But there are a lot of different ways to engage, to reach out, to ensure that people of a range of political support and backing know the vaccine is safe and effective."

Drew Angerer/Getty Images
White House Press Secretary Jen Psaki speaks during the daily press briefing at the White House on March 15, 2021, in Washington, D.C.

With such a large percentage of Americans not taking the vaccine, it will be difficult to reach the threshold of immunizations that could end the pandemic, which experts estimate to be somewhere between 70% and 90% of the U.S. population.

Fauci, though, said during a press briefing Monday that herd immunity is a rough estimate and that it may not be right, so it should not be the priority for now.

"We should not get so fixated on this elusive number of herd immunity," Fauci said. "We should just be concerned about getting as many people vaccinated as quickly as we possibly can."

ABC News’ Sarah Kolinovsky, Anne Flaherty and Will Steakin contributed to this report.