President Trump made the announcement during a video published on Twitter.
He said he was not feeling good when he first arrived at the hospital but he feels “much better now”.
Mr Trump tested positive for the coronavirus late on Thursday evening.
He was rushed to Walter Reed Medical Center on Friday following advice from his medical team.
Mr Trump thanked all the medical staff at the hospital in Maryland.
He said: “I came here, wasn’t feeling so well. I feel much better now.
“We’re working hard to get me all the way back. I have to be back because we still have to make America great again.
“We’ve done an awfully good job of that but we still have steps to go and we have to finish that job.”
Mr Trump revealed that he will “be back soon”.
The news of Mr Trump’s coronavirus diagnosis came just over a month away from November’s presidential election.
The president said he looks forward to finishing his election campaign.
Mr Trump said: “The way it was started and the way we’ve been doing. The kind of numbers that we’ve been doing. We’ve been so proud of it.
“But this was something that happened and it’s happened to millions of people all over the world and I’m fighting for them.
“Not just in the US, I’m fighting for them all over the world. We’re gonna beat this coronavirus.”
More to follow…