Fox News' Lucas Tomlinson pressed Kirby during a Pentagon news conference Saturday about his statement on Aug. 13 that "Kabul is not right now in an imminent-threat environment."
"How could you get that so wrong?" Tomlinson asked.
Kirby explained that he was sharing the best information he had at the time while acknowledging the public "ridicule." He said the situation in Afghanistan changed "dramatically" two days later but his comments at the time were an "accurate" reflection of the Defense Department assessment.
"In the moment that I said it, based on what we knew at the time, it was a true statement," Kirby said Saturday. "And yes, two days later, things dramatically changed. I readily admit that things moved very, very quickly."
Kirby added that "there wasn't any indication …. that things could evolve as quickly as they did."
In recent days, the Taliban swiftly took control of Afghanistan, setting off a chaotic and desperate situation for Americans and Afghan allies to rush to the Kabul airport to evacuate the country. About 6,000 U.S. troops are now in Afghanistan to aid with the evacuation effort at the airport.
As the chief spokesman for the Department of Defense, Kirby said Saturday he's "100%" committed to being as honest and transparent as he can from the press secretary podium when informing the American public.
After Kirby's response, however, a retired Army general sent a note to the Fox News reporter in the Pentagon briefing room that read: "His answer should have been ‘I was wrong.'"
Fox News' Lucas Tomlinson contributed to this report.