CNN— The American military had a “domain awareness gap” that allowed three other suspected Chinese spy balloons to transit the continental United States undetected under the Trump administration, the Pentagon general responsible for providing air and missile defense over North America said on Monday.

“Every day as a NORAD commander, it’s my responsibility to detect threats to North America. I will tell you that we did not detect those threats,” Gen. Glen VanHerck, commander of US Northern Command and North American Aerospace Defense Command said when asked about the three other balloons.

“And that’s a domain awareness gap that we have to figure out, but I don’t want to go into further detail.”

VanHerck added that the intelligence community after the fact was able to gather intelligence “from additional means that made us aware of those balloons that were previously approaching North America or transited North America.”

A senior administration official told CNN on Sunday that the intelligence community is prepared to offer briefings to key Trump administration officials about the Chinese surveillance program, which the Biden administration believes has been deployed in countries across five continents over the last several years.

Several senior officials from the Trump administration have not yet been contacted by the Biden administration about a briefing, people close to them told CNN on Monday.

Trump administration officials have insisted that they were not aware of any balloons transiting the US while Trump was in office.

“Did the Biden administration invent a time machine? What is the basis of this new detection?” John Bolton, a former national security adviser under President Donald Trump said, adding that he would take a briefing from the Biden administration if it was offered.

After the Biden administration disclosed last week that a suspected Chinese spy balloon was hovering over Montana, the Pentagon said that similar balloon incidents had occurred during the Trump administration. In response, former Trump administration Defense Secretary Mark Esper told CNN on Friday that he was “surprised” by that statement.

“I don’t ever recall somebody coming into my office or reading anything that the Chinese had a surveillance balloon above the United States,” he said.

Former President Donald Trump also said on Truth Social this week that reports of Chinese balloons transiting the US during his administration were “fake disinformation.”

National Security Council strategic communications coordinator John Kirby told reporters that there are several factors – like their altitude and speed – that make detecting the spy balloons difficult, saying that the ways to track them are “not constant.”

“They fly very, very high, very, very slow and in order to track, you’ve got to run the traps along many different lines of information and technology,” Kirby said. “Their dynamics, their trajectory, their flight behavior complicates the ability to know exactly where one is at any particular moment in time depending on where it is over the Earth’s surface.”

Delay in shooting the balloon down will be ‘well worth its value’

Adding to officials’ comments last week about the balloon that was shot down on Saturday’s ability to maneuver, Kirby said on Monday that the balloon had “propellers” and “a rudder … to allow it to change direction.” But that maneuverability was limited, he said, mostly restricted to “inside the jet stream.”

As far as size, the balloon was 200 feet tall, with a payload the size of a regional jet weighing over a couple thousand pounds, VanHerck said, which fed into concerns of what would happen if it was shot down.

“[Y]ou know from a safety standpoint, picture yourself with large debris weighing hundreds if not thousands of pounds falling out of the sky. That’s really what we’re kind of talking about,” he said. “So glass off of solar panels, potentially hazardous material, such as material that is required for a batteries to operate in such an environment as this and even the potential for explosives to detonate and destroy the balloon that could have been present.”

VanHerck clarified later that there was not reason to believe there were explosives on the balloon, but said it is an assumption officials have to make out of an abundance of caution.

Since the military operation on Saturday by F-22 fighter jets out of Langley Air Force Base in Virginia to take the balloon down, pieces of the balloon have since started arriving at the FBI’s lab at Quantico, Virginia.

And though there has been criticism that the balloon was allowed to linger for too long over the US, VanHerck said on Monday that he and the commander of US Strategic Command worked “in close coordination” and “took maximum precaution” to prevent Chinese intelligence collection.

The balloon was detected early enough to allow the US to gather intelligence on it while it transited the US before it was shot down, VanHerck said.

“There was a potential opportunity for us to collect intel where we had gaps on prior balloons,” he said. “And so I would defer to the intel community. But this gave us the opportunity to assess what they were actually doing, what kind of capabilities existed on the balloon, what kind of transmission capabilities existed, and I think you’ll see in the future that that time frame was well worth its value to collect over.”

CNN’s Josh Campbell, Kaitlan Collins and Sam Fossum contribted reporting.