President Trump flew by helicopter to Walter Reed National Military Medical Centre in suburban Washington to meet wounded service members and health care providers caring for Covid-19 patients.
As he left the White House, he told reporters: “When you’re in a hospital, especially … I think it’s expected to wear a mask.”
Mr Trump was wearing a mask in Walter Reed’s hallway as he began his visit, however he was not wearing one when he stepped off the helicopter at the facility.
The president was a latecomer to wearing a mask during the pandemic, which has so far infected more than 3.2 million and killed at least 134,000 in the US.
Donald Trump has been photographed wearing a face mask for the first time during a visit to a military hospital.
It is the first time the US president has been seen in public wearing the type of facial covering recommended by health officials to help stop the spread of coronavirus.
Most prominent Republicans, including vice president Mike Pence, endorsed wearing masks as the coronavirus gained ground this summer.
Mr Trump, however, has declined to wear a mask at news conferences, coronavirus task force updates, rallies and other public events.
People close to the president, speaking on condition of anonymity to The Associated Press, claimed he feared a mask would make him look weak and was concerned it would shift focus to the public health crisis rather than the economic recovery.
While not wearing one himself, Mr Trump has sent mixed signals about masks, acknowledging that they would be appropriate if worn in an indoor setting where people were close together.
President Donald Trump wears a face mask as he visits Walter Reed National Military Medical Centre in Bethesda, Md., 11 July 2020. (Patrick Semansky/AP)
But he has accused reporters of wearing them to be politically correct and has retweeted messages making fun of Democrat Joe Biden for wearing a mask.
The only time the president has been known to wear a mask was during a private part of a tour at a Ford plant in Michigan.
A long-expected surge in US coronavirus cases has begun, driven by deaths in states in the south and west of the country, new data shows.
The number of deaths per day from the virus had been falling for months in America, and even remained down as states like Florida and Texas saw explosions in cases and hospital admissions, while reported daily US infections broke records several times in recent days.
However, experts had predicted states that saw increases in cases and hospital admissions would eventually see deaths rise too, with fatalities typically taking place several weeks after a person is first infected.
According to data from Johns Hopkins University, the seven-day rolling average for daily reported deaths in the US has risen from 578 two weeks ago to 664 on 10 July – although this is still well below the heights hit in April.