President Trump on Saturday praised the staff at Walter Reed National Military Medical Center, and said he is "feeling well," a day after he was transferred to the center after testing positive for COVID-19.

"Doctors, Nurses and ALL at the GREAT Walter Reed Medical Center, and others from likewise incredible institutions who have joined them, are AMAZING!!!" he tweeted. "Tremendous progress has been made over the last 6 months in fighting this PLAGUE. With their help, I am feeling well!"

TRUMP DOING 'VERY WELL' AND HAS NO DIFFICULTY, BREATHING, MEDICAL TEAM SAYS 

Trump was moved to the medical center Friday evening in what was described as a precautionary measure after suffering symptoms the White House described as mild. He had announced his positive test result earlier Friday.

A number of White House and campaign officials have also tested positive – including senior White House adviser Hope Hicks and Trump campaign manager Bill Stepien. On Saturday former New Jersey Gov. Chris Christie, who was on Trump's prep team for Tuesday's presidential debate, announced that he had tested positive.

Trump's tweets came minutes after White House physician Dr. Sean Conley and other members of the medical team briefed reporters on Trump’s condition outside Walter Reed.

Conley said they were “extremely happy with the progress” Trump is making, having had a mild cough and some nasal congestion as well as fatigue. He described those symptoms as having been "resolved."

Dr. Sean Dooley, who is part of that team, said that Trump's cardiac, kidney and liver functions are all normal, and also that Trump is not on oxygen and is not having any difficulty breathing or walking.

The doctors also said Trump had been free of a fever for 24 hours. They also said he was on a five-day course of Remdesivir, having previously received an antibody cocktail, as well as zinc, Vitamin D, famotidine, melatonin and a daily aspirin.

Dooley described Trump as being in exceptionally good spirits and quoted him as having said: “I feel like I could walk out of here today.” However, they did not give a date for when Trump may leave the center.

Moments after the press conference, a source familiar with the president's health gave a more cautious diagnosis to the press pool.

"The president's vitals over last 24 hours were very concerning and the next 48 hours will be critical in terms of his care," the source said. "We are still not on a clear path to a full recovery."

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The president's reelection campaign announced Friday that his events are being temporarily postponed or moved to a virtual setting.

“All previously announced campaign events involving the president’s participation are in the process of being moved to virtual events or are being temporarily postponed,” Stepien said. “In addition, previously announced events involving members of the first family are also being temporarily postponed.”

Fox News' Brooke Singman contributed to this report.