US President Donald Trump is doing "very well" in hospital after his Covid-19 diagnosis, his doctors say, but their account has been disputed.
Dr Sean Conley said the president was not being given extra oxygen for now and had been fever-free for 24 hours.
But moments later, an official familiar with the president's condition expressed concern, saying Mr Trump was not yet on a clear path to recovery.
In exactly one month, Mr Trump faces Joe Biden in the presidential election.
The positive diagnosis, made public by the president in a tweet early on Friday, has upended his campaign and also cast doubt on his attempt to get a new Supreme Court judge confirmed before polling day.
The president is expected to remain at the Walter Reed National Military Medical Center close to Washington DC for several days. Dr Conley said he was "cautiously optimistic" but that he could not give a timetable for his discharge.
But the doctors' assessment was contradicted by an official who said some of his vital signs over the last 24 hours had been "very concerning" and that the next 48 hours would be critical. The official is a credible source who normally briefs reporters.
The president, being 74, a man and someone categorised as obese, is in a higher-risk category for Covid-19. He has so far been treated with an experimental drug cocktail injection and the antiviral medication remdesivir.
Writing on Twitter later, the president said: "Doctors, nurses and all at the great Walter Reed Medical Center, and others from likewise incredible institutions who have joined them, are amazing... With their help, I am feeling well!
What else did the doctors say?Speaking at a news conference on Saturday morning, Dr Conley refused to say whether the president had ever been on oxygen despite being repeatedly questioned. "None at this moment and yesterday with the team, while we were all here, he was not on oxygen," he said.
Shortly afterwards, several US media reported that doctors had given the president supplemental oxygen at the White House on Friday before deciding to transfer him to Walter Reed.
Dr Conley also said some of the president's symptoms including a mild cough and nasal congestion were "now resolving and improving", adding: "At this time the team and I are extremely happy with the progress the president has made".
There was also some confusion after he said the team were "72 hours" into the president's positive diagnosis. If confirmed, it would suggest Mr Trump attended two large campaign events possibly knowing he was infected.
Later in a statement released by the White House, Dr Conley clarified he meant to say "day three" instead of 72 hours, and said the president had been first diagnosed with Covid-19 on Thursday evening.
First Lady Melania Trump, who has also tested positive for Covid-19 and is isolating at the White House, was "doing great", Dr Conley said.