A car with US President Trump drives past supporters in a motorcade outside of Walter Reed Medical Center in Bethesda, Maryland on October 4, 2020.

US president Donald Trump made a surprise departure from Walter Reed National Military Medical Centre on Sunday evening, during which he was shown driving by cheering crowds of supporters.

CNN footage of the scene just outside the medical centre grounds shows Trump seated in the back of a black car, wearing a mask and a suit, waving to supporters.

In the latest update on the timeline for Trump's recovery, White House physicians told reporters Sunday morning the president was feeling better and they hoped he could be discharged on Monday.

Trump announced he was leaving the hospital in a video posted just moments before his motorcade was seen outside the medical centre.

In the video, he thanked the hospital staff and said he was going to "pay a little surprise visit to some of the patriots we have out on the street."

"They've been out there for a long time, and they've got Trump flags, and they love our country. I'm not telling anybody but you, but I'm about to make a little surprise visit," Trump said in the video. "Perhaps I'll get there before you get to see me."

Trump also remarked on his time since publicly revealing he tested positive for coronavirus and being admitted to the medical centre for treatment, which he said has "been a very interesting journey."

"I learned a lot about COVID," he said. "I learned it by really going to school. This is the real school. This isn't the 'let's read the book' school. I get it, and I understand it. And it's a very interesting thing, and I'm going to be letting you know about it."

Since Trump's diagnosis was made public early last Friday, representatives from the administration, campaign, and the hospital have issued contrary statements on the president's condition and treatment.

Business Insider's Connor Perrett previously reported that White House physician Sean Conley admitted at a Sunday press briefing that Trump was given supplemental oxygen on Saturday, which he dodged questions about from reporters one day earlier.

"I was trying to reflect the upbeat attitude that the team, the president, over his course of illness, has had," Conley said.

After the White House initially insisted that Trump was admitted to the hospital "out of an abundance of caution," White House Chief of Staff Mark Meadows said Sunday Trump experienced a "very concerning" period on Friday when his blood oxygen level dropped and he developed a high fever, The Associated Press reported. After those symptoms, Meadows said Trump was facing a "critical" 48-hour period in his recovery.

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