'They know': Donald Trump speaks out on mystery 'drones' in first post-election press conference

President-elect Donald Trump addressed the mystery drones flying over the East Coast of the US in his first post-election press conference.

He also described himself as a "big believer" in the polio vaccine, telling reporters that Americans won't lose it amid concerns his pick to lead the Department of Health and Human Services, Robert F Kennedy Jr., could seek to revoke its approval.

"You're not going to lose the polio vaccine. It's not going to happen," Trump told reporters at a wide-ranging news conference at his Mar-a-Lago resort.

READ MORE: Five dead including child after US Christian school shooting

Trump's comments come as Kennedy heads to Capitol Hill to meet with senators ahead of what could be a contentious confirmation fight. CNN previously reported that a lawyer associated with Kennedy has petitioned the US Food and Drug Administration to revoke approval of the polio vaccine used in the US.

Trump said that "everything should be looked at, but I'm a big believer in the polio vaccine."

He said that autism rates are much higher now than decades earlier, and that his administration will "look into" why. He added that he wants Kennedy to "come back with a report as to what he thinks. We're going to find out a lot."

But he also described Kennedy — the former Democrat who left the party to launch an independent 2024 presidential bid before ultimately dropping out and endorsing Trump — as a "very rational guy".

The president-elect on Monday took a measured tone, as he discussed meetings with pharmaceutical and tech company executives, Russia's war in Ukraine, the future of the Tik Tok app, inviting world leaders to his upcoming inauguration and more.

Here are other key lines from Trump's news conference:

READ MORE: UK court names alleged spy who forged close ties to Prince Andrew

View gallery

Conservative podcast host named as FBI deputy director under Trump

Drone sightings

Trump said he doubted that "drone sightings" across the Northeast in recent weeks were acts of a foreign power, but criticised President Joe Biden's administration for not revealing more details.

"Look, our military knows where they took off from. If it's a garage, they can go right into that garage. They know where it came from and where it went. And for some reason they don't want to comment. And I think they'd be better off saying what it is," Trump said.

He added: "Something strange is going on — for some reason, they don't want to tell the people — and they should."

READ MORE: Assad says he didn't plan to flee Syria, in first statement since escape

Federal agencies have faced intense pressure to give the public more details on unexplained sightings in the New York City metropolitan area and beyond that have been going on for weeks over residential neighbourhoods, as well as restricted sites and critical infrastructure.

Federal officials have said many of the sightings appear to be manned aircraft mistakenly identified as drones.

TikTok ban

Trump suggested he might reverse course on the impending ban on the social media app TikTok in the US.

"You know, I have a warm spot in my heart for TikTok because I won youth by 34 points and there are those that say that TikTok has something to do with it," he told reporters.

(Trump lost 18-29-year-old voters to Vice President Kamala Harris by 11 points, according to exit polls.)

Trump also credited interviews with podcasters like Joe Rogan for GOP gains with young voters, but said TikTok "had an impact so we're taking a look at it."

DOWNLOAD THE 9NEWS APP: Stay across all the latest in breaking news, sport, politics and the weather via our news app and get notifications sent straight to your smartphone. Available on the Apple App Store and Google Play.