His continued opposition to wearing a mask came as an ABC News/Ipsos poll found an overwhelming majority of Americans said they had worn a face mask in public in the last week.
The president taped a town hall-style interview with Fox News host Sean Hannity on Thursday afternoon at an airplane hangar in Green Bay, Wisconsin, at which the network required all attendees to wear masks and have their temperature checked upon arrival.
Trump was not wearing a mask in a short clip from the town hall that aired Thursday afternoon on Fox News, which hosted the event scheduled to air later in the day.
Earlier Thursday, the president visited the Korean War Veterans Memorial in Washington to commemorate the 70th anniversary of the start of that war. He and first lady Melania Trump stood relatively close to elderly veterans and other dignitaries, none wearing a mask, although a White House spokesman told ABC News the veterans had been tested for COVID-19.
The mask requirement at the Wisconsin town hall, instituted by Fox News, stood in marked contrast to the two large-scale events the president attended over the past week, both of which featured large, indoor crowds not required to wear face coverings or practice social distancing.
At a campaign rally in Tulsa, Oklahoma, on Saturday, a tiny percentage of the over 6,000 attendees wore masks as they sat and stood packed together inside an arena.
In Phoenix on Tuesday, Trump similarly spoke to thousands of young supporters who largely went without masks as they sat and cheered shoulder to shoulder inside a church. One Arizona public health expert told ABC News the event "could lead to a super-spreader event."
All three states hosting Trump have over the past two weeks seen increasing numbers of coronavirus cases, as well as higher rates of people testing positive. Oklahoma on Wednesday reported its highest single-day increase in cases, and over the last week, Arizona has experienced a record number of hospitalizations.
While Trump has never worn a mask in public, Vice President Mike Pence has -- albeit just on occasion and depending on the circumstances.
On Thursday in Ohio, he donned one when talking with community members at a police station, but he did not wear one at a presentation of an electric pickup truck just before. He had drawn flak for not putting one on when visiting the Mayo Clinic in Minnesota in April -- the facility required them for visitors -- and has since been spotted wearing one after a top aide tested positive.
Meanwhile, on Capitol Hill, there were signs top Republicans had started to increasingly embrace face coverings. In some states represented in the Senate by the GOP, the virus's spread has picked up in recent weeks as state and local authorities relax social distancing requirements.
Echoing some Republican governors who have increasingly encouraged -- but stopped short of mandating -- face coverings to stem upticks in their states, Senate Majority Leader Mitch McConnell on Thursday would not say that he thought masks should be required, but that he thought people "ought to" wear them.
"That's what we're doing in the Senate and what I'm counseling other people to do," he said.
Across the country, more Americans have started wearing masks in public, according to the ABC News/Ipsos poll published Thursday.
Nearly 9 in 10 Americans (89%) who left their home in the last week said they wore a face mask or a face covering -- up 20% since the last time the question was asked in mid-April.
Polls have shown Republicans wear masks at a lower rate than Democrats do. The latest ABC News/Ipsos poll found that, among those who have left their home in the last week, 99% of Democrats chose to wear a covering in public, compared to 79% of Republicans and 87% of independents.
Still, an overwhelming majority of Republicans said they had worn one.
The presumptive Democratic presidential nominee, former Vice President Joe Biden, has made a habit of wearing a mask in public, in stark contrast to Trump.
While the White House briefly required workers in the West Wing to wear face coverings after two staffers there tested positive for the coronavirus, the policy was only followed for a number of days before most staffers there stopped wearing them.
The White House says that because those who are in close proximity to Trump and Pence receive frequent or even daily tests -- like senior aides, outside guests visiting for meetings, and some members of the press -- masks are less necessary than they would be for members of the general public.
ABC News' Arielle Mitropoulos, Allie Pecorin, Trish Turner and Jon Garcia contributed to this report.