President Donald Trump has said he doesn't particularly believe that UFOs are extraterrestrial, but acknowledged that the military is on the look out.

Trump's remarks came in an interview with George Stephanopoulos airing on ABC News on Sunday.

Stephanopoulos pressed the president on a recent rise in US Navy pilots reporting unidentified aircraft, asking what Trump made of it.

'I think it's probably -- I want them to think whatever they think. They do say, and I've seen, and I've read, and I've heard. And I did have one very brief meeting on it. But people are saying they're seeing UFOs. Do I believe it? Not particular,' Trump said.

Trump told ABC News' George Stephanopoulos (right) that he has been briefed on UFO sightings, but is not particularly convinced that they are real

An image from footage shot by the Navy that shows an encounter between US fighter jets and 'anomalous aerial vehicles' flying at 25,000 feet

Asked if he thought he would know if extraterrestrial life had been confirmed, president replied, 'Well, I think my great pilots would know. Our great pilots would know.'

'They see things a little bit different from the past. So we're going to see. We're watching, and you'll be the first to know,' he assured Stephanopolous.

It comes as Navy pilots increasingly report sighting anomalous aircraft that appear to defy the laws of physics, prompting the service to roll out new guidelines for reporting sightings last month - though none of the information will be made public.

A Navy spokesman told The Washington Post that the reporting on UFOs would fall under 'privileged and classified information' so that military aviation safety organizations can 'preserve the free and honest prioritization and discussion of safety among aircrew.'

The new guidelines for reporting UFOs have come in response to unknown, advanced aircraft flying into or near Navy strike groups or other sensitive military facilities and formations, the Navy said.

'I did have one very brief meeting on it. But people are saying they're seeing UFOs. Do I believe it? Not particular,' Trump said

The Navy made it easier for sailors to report UFO sightings amid fears that the mysterious unidentified flying objects could actually be 'extremely advanced Russian aircraft.'

After years of dismissing UFOs, the new guidelines are being introduced in response of a series of unexplained sightings of unrecognized and 'highly advanced' aircraft encroaching on Navy facilities and strike force formations, the department says.

'There have been a number of reports of unauthorized and/or unidentified aircraft entering various military-controlled ranges and designated air space in recent years,' a spokesperson for the Navy said to Politico.

The statement continued: 'For safety and security concerns, the Navy and the U.S. Air Force takes these reports very seriously and investigates each and every report'.

In recent years, there has been a need for a more formalized process of recording UFO sightings which greatly increased after World War II.

In 2017 the service said it had run a secret UFO office and spent $22 million over five years to study 'anomalous aerospace' threats.'

An Operations Specialist Seaman stands a lookout on the aircraft carrier USS Carl Vinson (CVN-70) in a file photo. The Navy has issued new guidelines for reporting UFO sightings

But for now, the data 'remains strictly within classified channels,' said Luis Elizondo, an intelligence officer who ran the Pentagon's Advanced Aerospace Threat Identification Program, which officially ended in 2012, according to The Post.

The Navy has pledged to update and reform their current policies for how reports of 'suspected incursions' are made to the correct authorities.

Former Pentagon official Luis Elizondo, who headed up the specialist department, revealed after his retirement that he thought the office was too nonchalant in their investigations of the unidentified aircraft.

'If you are in a busy airport and see something you are supposed to say something,' Elizondo told Politico. 'With our own military members it is kind of the opposite: 'If you do see something, don't say something.'

He added that many of the specialist crafts sighted were said not to have flags on their tails – or any tail at all – asking, 'What happens in five year if it turns out these are extremely advanced Russian aircraft?'

However, the Navy's new policy does not mean they believe their sailors have actually encountered alien spacecraft, but rather they believe the reported sightings shouldn't be instantly dismissed and are worthy of further investigation.