The U.S. has evidence of UFOs breaking the sound barrier without a sonic boom and making maneuvers impossible with known technology, the former Director of National Intelligence has revealed.

The revelations increased excitement about a forthcoming report detailing what the U.S. government has observed.

John Ratcliffe, who served as Donald Trump's Director of National Intelligence, said that many of the incidents still have no easy explanation.

'There are a lot more sightings than have been made public,' Ratcliffe told Fox News.  

'Some of those have been declassified.

'And when we talk about sightings, we are talking about objects that have seen by Navy or Air Force pilots, or have been picked up by satellite imagery that frankly engage in actions that are difficult to explain. 

'Movements that are hard to replicate that we don't have the technology for. Or traveling at speeds that exceed the sound barrier without a sonic boom.'