"I won't talk to you about what I know about it but it's very interesting. But Roswell is a very interesting place with a lot of people that would like to know what's going on."
Pushed by his son about whether he would ever reveal what he knows, Trump demurred, saying: "I'll have to think about that one."
Trump's comments come on the heels of the Pentagon releasing three short videos that showed "unidentified aerial phenomena".
The infrared footage had previously been released by a private company.
Former Senate Majority Leader Harry Reid tweeted that Americans "deserve to be informed" about UFOs following the Pentagon's move.
Reid arranged funding in 2007 to a US$22 million programme to investigate UFOs. The Pentagon confirmed its existence in 2017.
Reid tweeted: "I'm glad the Pentagon is finally releasing this footage, but it only scratches the surface of research and materials available. The US needs to take a serious, scientific look at this and any potential national security implications. The American people deserve to be informed."
Axios reports that the US Navy also confirmed an increase in UFO sightings in 2019. It introduced a new process to allow pilots to report sightings at the time.
Officials say that, while UFOs don't necessarily indicate extraterrestrial life, they raise concerns over aircraft flying near sensitive military facilities and military-controlled ranges.
The Navy is officially releasing them now, "in order to clear up any misconceptions by the public on whether or not the footage that has been circulating was real, or whether or not there is more to the videos," Pentagon spokeswoman Sue Gough said in a statement.
"After a thorough review, the department has determined that the authorised release of these unclassified videos does not reveal any sensitive capabilities or systems and does not impinge on any subsequent investigations of military air space incursions by unidentified aerial phenomena."
