A retired US Air Force officer claims he had a close encounter in a British forest nearly four decades ago.

Steve Longero revealed Monday that he was a witness to the infamous 1980 Rendlesham Forest incident in Suffolk, England — dubbed “Britain’s Roswell” — where military personnel claimed they saw a UFO during a stretch of three spacey December nights.

“I think it was something not from this world,” Longero told The Sun.

He was on duty Dec. 26, 1980, the first night sightings were reported.

“We had a very sophisticated alarm system and everything just went off,” he recalled.

Longero continued: “It was real kind of quiet and this thing hovering over the trees, and you were like kind of tracking it and like, ‘What is this?’ And it was like following, it was like watching us, that’s what it looked like to us. It seemed like something was watching us.”

He said the supposed UFO had fluorescent lights that were flickering red and green.

One of his fellow officers, Col. Charles Halt, recently released a book detailing their close encounter called “The Halt Perspective.”

“Col. Halt came afterwards, after all that was called in,” Longero told The Sun. “I remember him turning up. That’s when they kind of gathered everyone around and said, ‘This is what we are going to do’ and everybody kind of dispersed and did what they were told to do.”

“I remember we had a little briefing right there and everybody was just like, ‘We just could not believe what we were seeing,’” he added.

The UFO sighting came as the two NATO airbases in the area — Bentwaters and Woodbridge — were on high alert because of the Cold War.

There are various theories as to what was really out there spooking the US military, including that it was a Soviet spy satellite.

In 2005, the UK Forestry Commission used lottery funds to pay for a “UFO Trail” in Rendlesham Forest.

This isn’t the only time a government agency has come in contact with a UFO: