"The government knows what is happening," Trump said. "For some reason, they don't want to comment. And I think they'd be better off saying what it is our military knows and our president knows."

Trump, speaking at a press conference in Palm Beach, Florida, said, "I can't imagine it's the enemy," without going into specifics. He declined to answer whether he had received an intelligence briefing on the matter.

A Pentagon spokesperson, speaking with reporters earlier on Monday before Trump spoke, reiterated that the drones in question were not U.S. military one. The spokesperson added that the military was limited by law in what it could do to detect and track drones within the United States, unless there was a threat.

"Flying drones is not illegal. There are 1000s of drones flown around the U.S. on a daily basis. So, as a result, it's not that unusual to see drones in the sky, nor is it an indication of malicious activity or any public safety threat," Pentagon spokesman Major General Pat Ryder told reporters.

"The same applies to drones flown near U.S. military installations. Some fly near or over our bases from time to time. That, in of itself, is not unusual, and the vast majority pose no physical threat to our forces or impact our operations," Ryder added.

A spate of reported drone sightings that began in New Jersey in mid-November spread in recent days to include Maryland, Massachusetts and other states. U.S. officials said on Saturday that most of the sightings involved manned aircraft and that there was no evidence of a national security threat.

An FBI official told reporters that less than 100 of the over 5,000 reported sightings had turned out to merit further investigation, and all of the large fixed-wing reported sightings so far involved manned aircraft.

Trump's pick for national security adviser, Mike Waltz, said on Sunday that the drone sightings underscored gaps in U.S. airspace security that need to be closed.