The US Department of Defence said on Friday that it was setting up a task force under the navy to investigate UFO sightings.
With the creation of the Unidentified Aerial Phenomena Task Force (UAPTF), the Pentagon hoped "to improve its understanding of, and gain insight into, the nature and origins of UAPs," spokeswoman Susan Gough said.
The US military was concerned about aerial phenomena connected with its terrestrial adversaries rather than alien visitors.
Washington is concerned about China's spying capabilities, using drones or other airborne means.
"The mission of the task force is to detect, analyse and catalog UAPs that could potentially pose a threat to US national security," Ms Gough said.
The Pentagon takes "any incursions by unauthorised aircraft into our training ranges or designated airspace very seriously and examines each report," she said.
"This includes examinations of incursions that are initially reported as UAP when the observer cannot immediately identify what he or she is observing."
Deputy Defence Secretary David Norquist approved the establishment of the task force on August 4.
The US Senate intelligence committee in June said it wanted to regulate a Pentagon UFO programme, confirming the existence of an informal working group which was revealed by the New York Times in 2017.
In December 2017, the Pentagon acknowledged funding the secret multi-million-dollar programme to investigate sightings of UFOs, although it said it ended in 2012.
The announcement of a new task force came after the Pentagon in April officially released three videos taken by US Navy pilots showing mid-air encounters with unusual aircraft.
The grainy black-and-white footage was leaked and the navy acknowledged its pilots took it.
One of the videos was shot in November 2004 and the other two in January 2015.
In one, the weapons-sensor operator appeared to lose lock on a rapidly moving oblong object which suddenly accelerated away to the left and out of view.
In another video tracking an object above the clouds, one pilot wondered if it was a drone.