The USA President – who beat Mrs Clinton in the 2016 – made the admission during an interview with Fox as he continued his attempts to ramp up support ahead of the midterm elections on November 6.
Host Laura Ingraham asked Donald Trump: “Who’s your dream person to run against in 2020?” He replied: “So far, I like them all.”
When the host asked how he would feel if Hillary Clinton ran again, Mr Trump said: “I like her too. I’d be very happy with Hillary. I don’t see anybody that I wouldn’t enjoy running against.”
On Friday, Mrs Clinton sparked speculation she might join the race again in 2020 after admitting at an event she would “like to be President”, although quickly denied this would be in opposition to Mr Trump in two years.
A poll conducted by US political website The Hill and polling company HarrisX in September revealed 44 percent of voters would vote for Mrs Clinton, while just 36 percent would choose Mr Trump.
But the former Democratic candidate’s allies have been quick to play down any chance of her joining the Presidential race in 2020.
Her longtime advisor Philippe Reines told The Hill: “She is more likely to win Powerball.”
Another unnamed longtime confidante added: “She’s not running. I think it would be pretty damn clear if she was.”
They were also quick to make clear there isn’t anyone trying to push her into the 2020 race, and there are no internal talks about her possible candidacy.
The confidant added: “I think a lot of people definitely think she was screwed in this last election but no one is urging her to do this.
“That doesn’t mean people don’t think the world of her. But the point of it is, it’s not a real thing.”
Democrat and former Governor of Virginia Terry McAuliffe also poured cold water on Mrs Clinton joining the 2020 race, telling US television broadcaster MSNBC she will “never be in the ballot again”.
He said: “It’s hard for Hillary. She got three million more votes than Donald Trump did in the last presidential election.
“But I feel confident in saying I think Hillary is never going to be on the ballot again. I think she is done running for elected office.
“She’s going to be out helping candidates. But I feel very confident in saying she’s not going to run for president.”
Mr Trump has previously said Joe Biden, Vice President from 2009 until 2017, is his “dream” opponent.
Mr Biden, who launched presidential campaigns in 1988 and 2008 before dropping out of the race each time, has been touted as a possible contender again.
Other names being mentioned include Democratic Senators Elizabeth Warren, Cory Booker and Kamala Harris, as well as lawyer Michael Avenatti.
Ms Clinton was defeated in the 2016 presidential election, despite receiving nearly three million more votes than Mr Trump – 65,853,514 compared to 62,984,828.
But the current US President won 30 US states with a total of 306 electors – or 57 percent of the 538 available.
He also won two perennial “swing states” which typically decide an election, in Florida and Ohio, as well as three “blue wall” stronghold states in Michigan, Pennsylvania and Wisconsin – which the Republicans had not won wince the 1980s.