President Trump on Tuesday downplayed the importance of wearing masks, saying the administration's top scientists have changed their minds about it.

During a segment of the presidential debate focused on the COVID-19 pandemic, Trump was attacked by Democratic presidential nominee Joe Biden for his repeated questioning about the effectiveness of masks.

"Masks make a big difference," Biden said, citing Centers for Disease Control and Prevention (CDC) Director Robert Redfield's recent statement that masks are the best defense available against the coronavirus.

"[Trump's] own head of the CDC said if everybody wore a mask and social distanced between now and January we'd probably save up to 100,000 lives," Biden said.

Trump then suggested that his health officials have changed their minds, noting that the CDC has not always recommended the use of face coverings.

"Dr. [Anthony] Fauci said the opposite, he very strongly said masks aren't good and then he changed his mind, he said masks are good," Trump said.

The CDC's messaging on masks has changed since the early days of the pandemic. Initially, health officials said face coverings were not needed to protect against the coronavirus. That recommendation was changed in early April, and ever since top health officials have consistently said masks can save lives.

Fauci, a member of the White House coronavirus task force and director of the National Institute of Allergy and Infectious Diseases, has said the initial recommendation against masks was a mistake, and was meant to conserve critical personal protective equipment.

Earlier this month, Redfield told Congress that wearing a mask could be a more effective tool to guard against the virus than a vaccine. Later that day, Trump said during a White House press conference that Redfield was mistaken and that he called up Redfield to chastise him over his testimony.

During Tuesday's debate in Cleveland, Trump said he wears a mask when needed, but added that everyone in the debate hall had already been tested for COVID-19 and was seated physically distanced from each other.

In the audience, a handful of people, notably Trump's children, were not wearing masks.

Under Ohio law, all individuals are required to wear a mask indoors when not at home.

According to pool reports, at one point a Cleveland Clinic doctor started to approach Trump family guests to offer them masks to wear. None of them ended up putting one on.

The candidates also clashed over campaign style, as Trump has held massive rallies both indoors and outdoors in airplane hangers. The president held an indoor rally in Nevada earlier this month.

Trump defended the rallies, saying most of them have been held outside, even though many have included thousands of attendees with limited physical distancing and masks.

Biden called it an "irresponsible" method of campaigning.