US President Donald Trump will resume in-person campaigning on Saturday (Oct 10) after being sidelined by a case of COVID-19, but a debate next week against his presidential election opponent Joe Biden has been cancelled.

Trump will address a crowd of supporters on Saturday from a White House balcony on a "law and order" theme, an administration official said. A source familiar with the planning for the event said the crowd could be in the hundreds, and all were expected to wear masks.

The Republican president will then travel on Monday to central Florida, a state crucial to his hopes of winning a second term in the Nov 3 election.

He will stage his first campaign rally at an airport in the town of Sanford, less than two weeks after he tested positive for COVID-19. The campaign did not disclose if it would be held in a hangar with doors open, as it has in the past, or entirely outside.

As the president prepared to return to the trail, the body that oversees presidential debates said the match-up between Trump and Biden, the Democratic candidate, scheduled for Oct 15 has been formally cancelled.

Trump refused to participate in what was supposed to be the second of three debates with Biden after the Commission on Presidential Debates switched it to a virtual contest in the wake of the president's illness.

The final debate on Oct 22 is still set to take place.