The US Pentagon has admitted to funding a project investigating unidentified flying objects (UFOs), for the first time.

The $22m (£17m) Advanced Aerospace Threat Identification Programme (AATIP) was established in 2007, and only a small number of senior officials knew about its activities, according to a report in the New York Times.

Former Democrat Senator Harry Reid of Nevada – home of the mythologised "Area 51" – was the driving force behind AATIP, which analysed reports of UFO sightings and collected audio and video evidence of mysterious aircraft.

"If anyone says they have the answers, they're fooling themselves," Reid said, in a tweet. "We don't know the answers but we have plenty of evidence to support asking the questions."

The Pentagon says it discontinued funding for AATIP ended in 2012 but insiders claim that its investigations continue.

A video released by the US Defence Department shows an encounter between US Navy aircraft and a UFO over San Diego in 2004.

The UFO is a round, white object roughly the size of a commercial passenger jet, speeding through the sky and rotating.

Navy personnel monitoring its progress are audibly stunned by the vessel. However, experts warn that there could be a number of non-extraterrestrial explanations for unusual sighting of this nature.

Sara Seager, an astrophysicist at M.I.T. said: "When people claim to observe truly unusual phenomena, sometimes it's worth investigating seriously... [but] "what people sometimes don't get about science is that we often have phenomena that remain unexplained."

UFO aliens
An artists Impression of a UFO LloydCanningsArt/facebook

James E. Oberg, a former NASA space shuttle engineer added: "There are plenty of prosaic events and human perceptual traits that can account for these stories. Lots of people are active in the air and don't want others to know about it. They are happy to lurk unrecognized in the noise, or even to stir it up as camouflage."

Earlier this year, the US Central Intelligence Agency (CIA) released a huge tranche of declassified documents online, including records of UFO sightings and a series of reports on flying saucers.

But this weekend's revelations are the first time the US Defence Department has admitted to funding research into the paranormal.

Former Senator Reid in a recent interview said: "I'm not embarrassed or ashamed or sorry I got this thing going. I think it's one of the good things I did in my congressional service. I've done something that no one has done before."