▶ Watch Video: Biden’s national security adviser Jake Sullivan on evacuating Americans from Afghanistan

President Biden’s national security adviser, Jake Sullivan, said the president believes U.S. forces will be able to get all Americans who want to leave Afghanistan out of the country by Mr. Biden’s self-imposed deadline of August 31. However, Sullivan said the U.S. does not know exactly how many Americans are in the country. 

“The president is committed to ensuring that every American who wants to leave Afghanistan gets out of Afghanistan. He believes that we can accomplish that by August 31,” Sullivan told “CBS Evening News” anchor and managing editor Norah O’Donnell on Thursday. 

Mr. Biden said Wednesday that U.S. troops could stay longer if all U.S. citizens who want to leave the country have not been able to do so by the deadline. 

“Americans should understand that we’re going to try to get it done before August 31,” Mr. Biden told ABC News. “If we don’t, we’ll determine at the time who’s left. And if there are American forces, if there are American citizens left, we’re going to stay to get them all out.”

Sullivan said the U.S. has the capacity to fly thousands of people from the Kabul airport to other countries each day. It’s the responsibility of those fleeing to get to the airport themselves.

“We have plenty more seats on flights than we believe that there are possibly Americans still in Afghanistan, and there is plenty of time to get to the airport. So, yes, we believe that over the course of the coming days, it is completely feasible for us,” he said. 

But it’s unclear precisely how many Americans are stranded in the country. 

“The U.S. government doesn’t actually know the precise answer to that question and that’s because we ask every American who comes to Afghanistan to register with the U.S. Embassy. But when people leave, they often don’t deregister, and even some who come never register in the first place.” 

O’Donnell asked Sullivan how the administration can make sure every American is out of the country if they don’t know how many are there. 

“One, is the entire database of Americans that we have in Afghanistan. And we can go to them through every means of contact we have and reach out and say, if you want to come home, if you want to get out, come to the airport,” he said. “The second way is to broadcast through every means available — radio, television, the internet — to reach Americans so they have the information they need to be able to come home.” 

Sullivan said the U.S. is “mindful” of the risks facing U.S. personnel if they are not out of Kabul in 12 days, calling it a “dynamic and dangerous situation.” He said the U.S. has made clear to the Taliban that if they prevent Americans from leaving, “they will be met with a swift and forceful response.” 

As it toppled the Afghan government, the Taliban seized U.S. military equipment that was intended to aid its Afghan allies. Sullivan said the Defense Department is working to account for the equipment that may now be in Taliban hands. 

“The Afghan military requested from the United States capabilities to be able to fight the Taliban. So the president had a choice: Say no and leave them without those capabilities, or say yes and run the risk that if they lost they fall into the hands of the Taliban. Neither choice was a perfect choice but he made the one he thought was in the best interest of our country,” Sullivan said. “And that’s why we find ourselves in the situation we do today.”