(CNN) The US military is advising President Joe Biden that he must decide by Tuesday whether to extend the evacuation in Afghanistan beyond August 31, according to a defense official directly familiar with the discussions, though Biden has yet to make a decision.
Military advisers have told the White House that the decision must be made by Tuesday in order to have enough time to withdraw the 5,800 troops currently on the ground, as well as their equipment and weapons. If the President agrees, the military anticipates "a few more days" of trying to evacuate as many people as possible before the drawdown of US forces begins, possibly at the end of this week.
As of Monday, Biden was still deciding whether to extend the deadline for removing all US troops, CNN has learned. Several of the President's advisers have advised against an extension, citing the security situation on the ground. Officials have spent recent days monitoring potential terrorist threats, citing "persistent" and credible information that the chaotic situation outside the airfield has created a target for ISIS-K and other organizations.
The Pentagon's decision-making ultimatum for Biden follows the Taliban's declaration that the US must remove all forces by August 31 -- a deadline that US military officials say they are still currently planning to meet, with an accelerated pace of evacuation flights now taking thousands out of Afghanistan every day and the US military even entering Kabul, as necessary, to retrieve people. While senior US national security expressed optimism that there will be no need to extend beyond August 31, Biden has said that if need be, the mission to extract US citizens and some Afghans could continue into September.
For now, Pentagon spokesman John Kirby said the military is working with an August 31 deadline in mind. "That is the mission we've been assigned by the commander in chief ... that's what we're trying to execute," Kirby told reporters at a briefing Monday.
Earlier that day, a Taliban spokesperson said that if US troops were still in the country after that, "our leadership will take proper and necessary decision[s]."
Biden told reporters on Sunday that "there's discussions going on in the military about extending. My hope is we will not have to extend." He said the decision might depend "on how far along we are in the process" of evacuating Americans. The President is also expected to encounter a push from allies to extend the deadline during a Tuesday morning virtual meeting of G7 leaders.
Biden was asked what he will say if G7 leaders -- who are expected to press him to extend -- ask the US to stay longer. "We'll see what we can do," he said he would tell his counterparts.
National security adviser Jake Sullivan expressed optimism that the US will be able to get all Americans who want to leave the country out before the August 31 deadline. "In the days remaining, we believe we have the wherewithal to get out the American citizens who want to leave Kabul," Sullivan said during a White House news briefing on Monday.
With the clock ticking down, the Pentagon said Monday that US and coalition aircraft had evacuated approximately 16,000 people from Kabul within the last 24 hours, with the US military transporting just under 11,000 of them.
US officials have declined to say how many Americans have been evacuated, but according to a source familiar with an administration "SitRep" report, as of 7:30 a.m. ET Monday the evacuation operation had flown 4,293 American citizens out of Afghanistan since the US flights began.
The source said the report shows 369 Americans had been "manifested since midnight Kabul time" that day, speaking to the 24-hour nature of the effort. The report also notes that 1,000 US citizens have been contacted about traveling to the airport for processing, "but a portion may be outside of Afghanistan."
Sullivan told reporters Monday that one reason the US can't be certain how many Americans are in Afghanistan is that they're not required to register their presence with the embassy when they enter the country or to advise the embassy when they leave.
The source familiar said the report says that "since beginning of operations" 20,156 Afghans have been evacuated along with 642 third country nationals or people of unknown origin. State Department spokesperson Ned Price said Monday that they are not sharing this information publicly because they do not want to give out rough or outdated information.
As the evacuation proceeds, Sullivan said the US is in touch with the Taliban daily through both political and security channels. He cautioned that regardless of Taliban warnings, it will be Biden's decision, and Biden's alone, whether to keep any US troops in Afghanistan past the end of the month to assist in evacuations.
"As I said, we are engaging with the Taliban, consulting with the Taliban on every aspect of what's happening in Kabul right now. ... We'll continue those conversations with them. Ultimately, it will be the President's decision how this proceeds, no one else's," he said.
As the mission to evacuate US citizens, visa applicants and other vulnerable Afghans accelerated dramatically over the weekend, the Pentagon said Monday that the US military has been entering the city of Kabul to extract stranded people and take them to the airport as needed.
Kirby stressed that these instances are not occurring on a "regular" basis, but "on occasion, when there's a need and there's a capability to meet that need, our commanders on the ground are doing what they feel they need to do to help Americans reach the airport."
Apart from a previously reported situation where four US military Chinook helicopters extracted 169 people from the roof of the Baron Hotel and transported them to the airport last Thursday, there has been "one additional instance" where helicopters have been used to take evacuees to the Kabul airport, Kirby said.
He did not provide details about where and when this instance occurred but said additional troops will not be sent in before August 31 to assist with these types of extraction missions.
Last week, Secretary of Defense Lloyd Austin said the US troops based at the airport did not have the ability to go into the city to retrieve "large groups" of people who needed to get to the airfield.
Speaking to the August 31 deadline, Sullivan told reporters Monday that "the question is, are we on track to fulfill our objectives of this operation? To bring out our people, so many of those Afghans who helped us and so many of those Afghans at risk, and we believe we are."
But Afghans employed by the embassy have told CNN that their attempts to get to the airport and leave the country have been brutally draining and unsuccessful, or they have managed to reach the airport but have been bloodied and mentally distraught in getting there.
Asked about their accounts, and their attempts to reach evacuation flights, State Department spokesperson Price said that locally employed staff "are absolutely a priority."
"They are absolutely part of our plans. And that commitment to them, to their safety and security, is something that is in no way diminished," he said at a news briefing on Monday. Price said they have been able to relocate members of the locally employed staff but did not give specific numbers.
Price claimed that locally employed staff at the US Embassy in Kabul had not been evacuated to the airport with American personnel "just because they weren't at the embassy compound by and large that day."
"When the embassy was evacuated and our personnel started to make their way from the embassy in Kabul to the secure facility on the airport compound, many if not all of our locally engaged staff were not present on the embassy compound at that time. They were working remotely given the volatile security situation; many were at home, were not at work," he said.
CNN reported last week that the embassy on Wednesday sent a notice to the thousands of locally employed staff telling them they can go to the airport for an evacuation flight, but some of the Afghans who made it into the airport were bloodied and distraught, having lost most of their belongings along the way, according to multiple sources familiar with the matter.
Others decided they didn't even want to pursue the perilous journey, though they desperately want to get out of the country. Still others who did take the risk had to turn back after facing untenable situations.
"I decided I would rather the Taliban shoot me in the head to being stuck in that situation," said one Afghan who worked at the embassy for years, in describing his journey to CNN.
This story has been updated with additional reporting.