(NewsNation) — David Grusch, who previously testified before Congress that the U.S. has a secret UFO retrieval program, defended those claims in a new interview with the BBC.

A top Pentagon official called the UFO hearing in July “insulting” to employees who are investigating sightings. Dr. Sean Kirkpatrick’s letter, published on his personal LinkedIn page and circulated Friday across social media, criticizes much of the testimony from Grusch that energized believers in extraterrestrial life and produced headlines around the world.

Kirkpatrick also claimed that Grusch never worked for the office of the Pentagon that’s responsible for investigating UFOs.

“Dr. Kirkpatrick oversaw our activities and what we were doing and the money we were spending,” Grusch told the BBC. “I never said I was a part of the core team, so I believe it was just lost in translation or misconstrued.”

Grusch, a retired major in the Air Force, testified that the U.S. has concealed what he called a “multi-decade” program to collect and reverse-engineer “UAPs,” or unidentified aerial phenomena, the official government term for UFOs.

NewsNation has confirmed Grusch’s credentials and resume, but has not seen or verified the alleged proof he said he provided to investigators. Grusch said he can’t show NewsNation the evidence for national security reasons.

The Associated Press contributed to this report.