In a show of medical brinkmanship, US President Donald Trump made his first public appearance at a White House event, 10 days after he was diagnosed with the novel coronavirus.

During Saturday's event at the South Lawn, titled "Peaceful Protest in Support of Law and Order", the President addressed the attendants, many who did not wear masks or were socially distancing, from the Blue Room Balcony.

Trump wore a face mask but took it off later when he started addressing the gathering.

Trump, who has downplayed the seriousness of the pandemic to the nation and himself, showed no signs of the disease, but uncharacteristically his speech was about 18 minutes, as opposed to his previous 60-minute speeches at other events and rallies.

He spoke with a strong voice and his breathing appeared steady with no lingering signs of the disease except for a bandage on his right hand, probably from the medicines he received intravenously during his stay at the Walter Reed National Military Medical Center for three nights.

The gathering was an outreach to the African-American community by Trump who has been accused by his critics of being hostile to minorities, if not racist.

He hopes to attract them with his criminal justice reform undoing some of the harsh sentencing requirements that his Democratic rival Joe Biden was involved in drafting that came down disproportionately hard on members of that community.

His campaign also points to Democratic Vice Presidential candidate Kamala Harris's record as a prosecutor who jailed large numbers of African-Americans for minor crimes.

Labelling the event a "protest" was to mock the Democratic Party's support for demonstrations against racial injustice and police brutality meted out to the African-Americans.

The event was organised by a group called BLEXIT, which according to its African-American founder Candace Owens stands for Black Exit from "permanent victimhood" with self-confidence for achievement.

She has also said it stands for exit from the Democratic Party, which has had near monopoly on African-American votes.

Addressing the event, Trump said: "Sleepy Joe Biden has betrayed black and Latino Americans. If you think he can run this country, you're wrong."

He was also trying to appeal to the demands by some African-American leaders for better law enforcement after a spike in crimes that hit minority communities following the anti-police protests with an agenda for cutting funds for police and even abolishing police.

African-Americans and Latinos are embracing his "pro-police — we want law and order; we have to have law and order — and pro-American agenda", Trump asserted.

"If the left gains power, they'll launch a nationwide crusade against law enforcement,' he said, adding added that "homes, churches and businesses" of minorities have "been vandalized and burned by left-wing fanatics".

Trump further accused the Democrats and Biden of getting Wall Street money and being beholden to them.

The event came after Trump's personal physician Sean Conley cleared him on Thursday for public engagements starting on Saturday "based on the trajectory of advanced diagnostics the team has been conducting".

Ending the 10-day isolation after Covid-19 diagnosis was in conformity with the Centers for Disease Control minimum guideline, but it also said some patients may still be producing the virus and may need to be isolated for up to 20 days.

After the rally, Conley issued a memo saying that Trump's tests in the morning showed that under "currently recognised standards, he is no longer considered a transmission risk to others".

With the clock ticking on Saturday at 24 days to the November 3 election, Trump was desperate for getting out to campaign having lost 10 precious days of electioneering.

The President is scheduled to hold at least three in-person rallies this week, beginning on Monday in Florida.

Also on Saturday, Biden held a Covid-19 precautions-compliant meeting in Erie, Pennsylvania, outside a trade union training facility.

The participants all wore masks and sat in socially-distanced chairs.

"If every investment banker in New York went on strike, nothing would much change in America, but if every plumber decided to stop work, every electrician, the country comes to a halt. I mean literally, not figuratively, literally comes to a damn halt," the former Vice President said.

Biden further said that if he was elected, "there's going to be such a race for job creation for unions, you're not going to believe it"..