Standing alone and not wearing a mask, Trump spoke from the White House balcony at an event on Saturday called "a peaceful protest for law and order," attended by a few hundred people standing on the lawn below.
His appearance is seen as a first step toward resuming full campaigning next week. As well as a rally in Florida next week, he added two more - in Iowa and Pennsylvania.
Speaking without hesitation, Trump appeared to be back to his usual rallying form, boasting about his record and hurling unsubstantiated allegations against his opponents as a packed crowd of supporters chanted, "We love you."
It was the first public event Trump has held since he was released from the hospital on Monday, when some observers watching his return to the White House said he appeared at times to be short of breath.
The White House has released videos and Trump has called into television shows since then, but this was the public's first chance to see the president live.
The White House has not released the results of Trump's latest Covid-19 test, and has declined to say when he last tested negative.
Scott Atlas, the doctor advising Trump, declined to comment on Trump's last test when approached by Reuters outside the event cordon. He was not wearing a mask.
Trump, who has campaigned on a law-and-order theme during recent months of sometimes violent protests for racial justice, told Saturday's gathering that the Republican Party had the support of America's police forces.
"We have law enforcement watching," he said. "We're on the side of right."
Trump's efforts to portray himself as tough on crime have had little impact on his standing in national opinion polls, which show him trailing his Democratic challenger Joe Biden by double digits.
But the gap between the two candidates is narrower in the battleground states that may determine who wins the White House on November 3.
