President Biden's National Security Adviser Jake Sullivan on Sunday admitted that the administration still does not know how many Americans are in Afghanistan.

CNN "State of the Union" host Brianna Keilar asked Sullivan if he could tell her how many Americans and legal permanent residents are still waiting to be evacuated in Afghanistan.

BIDEN SAYS 'WE WILL GET YOU HOME' TO AMERICANS TRAPPED IN AFGHANISTAN EXIT, BUT NOT SURE HOW MANY STILL THERE

"We cannot give you a precise number," Sullivan said. "We believe it is several thousand Americans who we are working with now to try to get safely out of the country."

He then blamed Americans not registering or deregistering properly at the U.S. Embassy in Kabul for why they do not know the exact number.

"The reason we can't give you a precise number is that we ask Americans, when they come to Afghanistan, to register with the embassy. Many come and do that, but then they leave and never deregister," Sullivan said. "Many others come and don't register at all. That is their right. It was their right, of course, to remain in Afghanistan as long as they wanted and it's our responsibility to get them out."

Sullivan isn't the only Biden administration official who hasn't been able to answer questions about the number of Americans in Afghanistan. Last week, Pentagon spokesman John Kirby said, "I don't know" in response to the same question and then was pressed again in a follow-up question asking how the Biden administration doesn't know these numbers.

AMERICAN MOM TRAPPED BY TALIBAN DESCRIBES HORRIFIC VIOLENCE, PLEADS FOR BIDEN TO SOLVE EVACUATION CRISIS

"I think as you probably know, first of all, the State Department would be a better place to go for an estimate of how many Americans are in Afghanistan or in and around Kabul. That is not a figure that the United States military would know, and I think you also know not every American citizen in another country that there’s no obligation that they register their presence. And that you can have a perfect accurate count," Kirby said.

However, when State Department Spokesman Ned Price was asked later that day about the number of Americans still waiting to be rescued in Afghanistan, he replied, "We’re just not in a position to give a number right now."

"We’re more broadly, not in position to offer an aggregate figure, because we are putting forward offers to individuals who may be interested in relocating," Price added.

CLICK HERE TO GET THE FOX NEWS APP

Despite not knowing how many Americans are still in Afghanistan, Biden on Friday said, "Let me be clear, any American who wants to come home, we will get you home."

"Make no mistake, this evacuation mission is dangerous and involves risks to our armed forces. And it's being conducted under difficult circumstances. I cannot promise what the final outcome will be, or what it will be that it will be without risk of loss.," Biden continued. "But as commander in chief, I can assure you that I will mobilize every resource necessary."

Fox News' Tyler Olson contributed to this report.