The operation entails "a full marshalling of top-level surrogates, campaign coalitions and supporters" to keep up the bid for Trump to be re-elected for a second term, in the November vote.

Vice President Mike Pence and Trump's family will be prime players in the effort, which will feature a series of online events leading up to Wednesday's vice presidential debate before moving to in-person events.

Pence outlined the effort in an all-staff conference call Saturday afternoon with campaign manager Bill Stepien, who has also been diagnosed with COVID-19.

"I want to encourage you to stay in the fight," Pence told the staff.

Meanwhile Donald Trump says he's "feeling well" and has voiced his appreciation for the medical professionals treating him for COVID-19 at a military hospital.

On Saturday, Trump tweeted, "Doctors, Nurses and ALL at the GREAT Walter Reed Medical Center, and others from likewise incredible institutions who have joined them, are AMAZING!!!"

He also says, "With their help, I am feeling well!"

White House chief of staff Mark Meadows said Trump went through a "very concerning" period Friday and the next 48 hours will be critical in terms of his care.

Australian Associated Press