Washington (CNN)Sitting alongside Afghanistan's President in the Oval Office last week, President Joe Biden didn't try to sugarcoat the situation: Things were not looking great for his guest's country.
"Every time I think I've got a tough job," Biden said ruefully, gesturing toward Ashraf Ghani, "I think, Mr. President?"
Ghani managed a polite laugh in response, adding a brief moment of levity to a tough conversation.
After nearly 20 years in Afghanistan, the US military, at Biden's direction, is in the final stages of withdrawing troops from the country, bringing an end to America's longest war.
The last US troops have left Bagram Air Base, according to a US defense official, marking the end of the American presence at the sprawling compound that became the center of military power in Afghanistan.
Three months after Biden announced his decision to draw down troops by September 11, the pace of withdrawal is catching some in Washington by surprise, yet there is no indication that Biden or any of his top aides are second-guessing the move. Sources inside the White House tell CNN that the President and his team have measured the political and national security ramifications of the decision and remain confident it's the right one.
But the grim consequences of withdrawal are only just starting to become clear. And while the White House remains united behind the decision, across the government concerns are rising about the deteriorating security in Afghanistan, the pace of withdrawal and the many questions that are still unanswered about America's long-term strategy.
Speaking at the White House on Friday, Biden grew visibly irritated when questioned about the state of the country US troops are in the process of leaving.
"I'm not going to answer any more questions about Afghanistan," Biden said after detailing his drawdown plans, his hopes for the embattled civilian Afghan government and his view of US air support.
"Look, It's the Fourth of July," Biden said, gesturing with his hands in exasperation. "I'm concerned that you guys are asking me questions that I'll answer next week. This is a holiday weekend. I'm going to celebrate it. There's great things are happening."
US intelligence services, military commanders and members of Congress are all warning that the Afghan government won't be able to stand up to the Taliban without the backing of American firepower. The Taliban are already moving rapidly to take over districts in the northern parts of Afghanistan, leading US military commanders to raise the prospect of a civil war once US troops are gone.
Other big decisions have yet to be made, including whether and how the US will use drones in the future to target suspected terrorists in Afghanistan, how to secure the civilian airport in Kabul and how exactly to ensure the safe passage of Afghan translators and other workers who assisted American forces during the war and are now targets for the Taliban.
Looming over everything is the potential -- increasingly likely, according to intelligence assessments -- that the Taliban will overwhelm Ghani's government and retake control of the country. Recent assessments have put the likely timeline of a Taliban takeover anywhere from six to 12 months, according to people familiar with the reports.
"We were in that war for 20 years," Biden said on Friday when questioned about the Afghan government's ability to resist Taliban offensives.
"I think they have the capacity to sustain the government," Biden said, adding negotiations with the Taliban -- currently stalled -- would likely have to resume. "I am concerned they deal with the internal issues they have to generate the kind of support they need."
Top military leaders had hoped to persuade Biden to maintain at least a small troop presence in Afghanistan, but they have now accepted his decision, according to several officials familiar with the matter. Biden's opposition to the war in Afghanistan is well-established. And now, after he fiercely questioned the war strategy as a US senator and clashed in the Situation Room with officials over troop levels as vice president during the Obama administration, the decision was finally his to make.
It was, and remains, a "gut decision," according to one US official familiar with Biden's thinking.
Despite being haunted during the decision process by the specter of American personnel being evacuated from Saigon in 1975, Biden remains convinced that after two decades of war, there is little American troops can do to resolve what is increasingly viewed inside the government as an intractable problem.
Indeed, the pace with which the Taliban have gained ground in recent weeks has, in a way, only solidified for the White House the merits of Biden's decision, according to multiple officials.
That the country's government could sit at the brink of failure in such an accelerated fashion, after 19 years of being trained, equipped and financed by America, gives credence to the idea that the long-term merits of maintaining a force presence in the country were limited, according to one official.
White House officials also say they were boxed in by the Trump administration and the agreement it had brokered with the Taliban, which they say would have eventually opened American troops to increased attacks.
"When the President made the announcement of our decision, it was in part based on a timeline that was committed to by the prior administration of May 1," White House press secretary Jen Psaki said on Wednesday. "And if we kept our troops in Afghanistan after May 1, they would be shot at."
Biden told Ghani in the Oval Office last week that while the US would boost its economic support, there was zero chance he would change his mind and keep forces in the country beyond a small contingent to provide security at the US Embassy. The US is planning to keep up to 1,000 troops in Afghanistan to guard the embassy in Kabul and the city's airport, though some officials insist the number will not top 650.
"Afghans are going to have to decide their future," Biden said. "The senseless violence has to stop, but it's going to be very difficult."
Concerns on Capitol Hill
The prospect that the US-backed government in Kabul could fall soon after American troops depart has raised concerns among lawmakers about a resurgence of terrorism in the country. Republicans and Democrats have repeatedly pressed the Biden administration for details about its plan for conducting counterterrorism operations in Afghanistan once the withdrawal is complete, which could be as soon as next week, according to multiple officials.
In May, a group of Republicans on the House Armed Services Committee wrote to Defense Secretary Lloyd Austin requesting that he provide a risk assessment of the conditions on the ground in Afghanistan. The Pentagon is legally required to provide that assessment to Congress before spending funds to draw down US military personnel in Afghanistan below troop levels of 4,000 and 2,000, according to the letter sent to Austin.
However, lawmakers were informed last week by Under Secretary of Defense for Policy Colin Kahl that Biden had granted a waiver, thereby allowing the Pentagon to move forward with the withdrawal without providing that assessment to Congress or answering a series of key questions about his plan for countering terrorists in Afghanistan going forward.
"The President was thoughtful and deliberate in considering a range of facts and advice before he made his decision to withdraw our remaining US forces from Afghanistan," Kahl wrote to the Republicans in a previously unreported letter obtained by CNN.
That response has frustrated Republicans, who maintain the administration has yet to explain how it plans to prevent Afghanistan from becoming a haven for terrorists.
"It's unfortunate the Biden Pentagon is unwilling to verify that our counter terrorism forces will be able to effectively continue their mission before withdrawing US forces and creating the circumstances for Al Qaeda and ISIS to come roaring back," according to Rep. Michael Waltz of Florida, one of the Republicans who signed the original letter to Austin.
Meanwhile, the administration is still only in the early phases of a policy review of Pentagon and CIA authorities to target terrorists overseas, including in Afghanistan, officials told CNN.
Republicans have warned that Biden will be held responsible for the aftermath of the withdrawal from Afghanistan, something they said they had joined with Democrats to prevent then-President Donald Trump from carrying out. Senate Minority Leader Mitch McConnell met with Ghani the day before the Afghan leader's White House visit and blasted the White House's withdrawal plans afterward.
"Increasing indications that this collapse could come soon after US withdrawal is complete are as tragic as they are avoidable," the Kentucky Republican said. "Ghani and the people of Afghanistan are entitled to wonder why the Biden administration has chosen to abandon the fight and invite even greater terrorist threats."
For many Democrats, there are lingering concerns that the Biden administration has not fully thought out how it will keep Afghanistan from becoming a haven for terrorists, and that the gains made for women's rights will be wiped out if the Taliban take charge. But many Democrats have argued that Biden's withdrawal is simply the best of a slate of bad options left to him by the Trump administration in Afghanistan.
Still, as the Taliban continue to gain, Democrats say they want to make sure the Biden administration is prepared for the potential repercussions.
Asked about the potential for the US to lose intelligence-gathering capabilities once the withdrawal is complete, House Intelligence Chairman Adam Schiff told CNN, "I think that there's no escaping it will be impacted, and the question is how successful can we be in working around those obstacles."
"I think they're doing everything they can to maintain visibility into what our adversaries are doing," the California Democrat added.
Rep. Elissa Slotkin, a Michigan Democrat who's a former CIA and Pentagon official, told CNN it's clear there will be a degradation of security but that the status quo in Afghanistan simply couldn't hold.
Plus, she added, popular opinion outside Washington is clearly on one side of the debate.
"The place where I hear a real debate about staying in, changing the plan, reversing the decision, is inside the Beltway," Slotkin said. "If you go back to my district, where veterans are sending their sons and daughters off to fight in the same war that they fought in, I think President Biden is in touch with popular opinion about this."
'Worst case: Civil war'
Military officials -- past and present -- have advocated for an American force to remain in Afghanistan to protect the US presence and support Afghan forces in keeping the Taliban at bay, warning of the consequences of a rapid, unconditional withdrawal.
As Taliban forces blitz through a growing number of districts in Afghanistan, US military officials' greatest fears may be realized before long.
"The security situation is not good right now," Gen. Scott Miller, the top US general in Afghanistan, told reporters on Tuesday. Instead of attacking coalition forces, the Taliban have carried out a brutal campaign against Afghan security forces, often launching upward of 100 attacks a day. The US has conducted airstrikes in support of Afghan forces, but even with foreign intervention Afghan forces have been able to take back only a small number of districts.
Miller told The New York Times this week that "civil war is certainly a path that can be visualized."
Former Joint Chiefs Chairman Gen. Joseph Dunford, co-chair of the Afghanistan Study Group created by Congress to examine the future of the country, argued in the final report issued earlier this year that it would take about 4,500 troops to secure US interests, including counterterrorism, embassy protection and more. Dunford, who commanded US forces in Afghanistan in 2013-2014, when there were more than 60,000 troops there, warned with the group that a rapid withdrawal was "likely to exacerbate the conflict, provoking a civil war."
Defense officials insist they were given the time and space to present their case to Biden on the importance of a small number of troops remaining in Afghanistan, meeting with him multiple times during the early months of the administration. And while they are all on board with executing his decision, some feel an understandable sense of discomfort with what lies ahead.
Testifying before the House Armed Services Committee last week, Joint Chiefs Chairman Gen. Mark Milley gave a bleak assessment of the country's future.
"The worst case: civil war, a breakdown -- fracturing of the government, fracturing of the army. That's very possible, and that would be a very bad outcome," Milley said. "There's also a possibility -- not high on the probability list -- but a negotiated settlement between the government and the Taliban. That's possible. And then the alternative is an outright takeover of the Taliban, which I also think is unlikely, but possible."
Evacuating Afghans still work in progress
With the possibility of a civil war or Taliban takeover looming, the White House is feverishly working to solidify a plan to evacuate thousands of Afghan nationals who have worked alongside US diplomats and troops over the past two decades. The task of organizing this effort falls almost entirely to the State Department. Some 18,000 Afghans have applied for visas, leaving US diplomats scrambling to figure out how and where to relocate them.
This is all happening as the US Embassy in Kabul is under lockdown due to a Covid-19 outbreak. The outbreak has added even more stress to the lives of US diplomats in the country, who tell CNN they are fearful about the future. They are not sure that the US Embassy will be able to remain open when the American troops withdraw.
State Department officials have told CNN that some of the Afghans who helped the US have been targeted for murder by the Taliban, and the concern is that their safety will be in even greater jeopardy as US troops continue to withdraw.
Lawmakers in both parties urged the Biden administration to commit to relocating these Afghans and have expressed frustration that the effort to evacuate them is quickly running out of time.
"The United States has a moral obligation to these Afghans and their families who face persecution and threats to their lives because of their support for Americans in Afghanistan," Senate Foreign Relations Chairman Robert Menendez wrote to Secretary of State Tony Blinken on Tuesday, urging the administration to move quickly.
The New Jersey Democrat used the letter to list a series of questions, many of which sought the most basic of details, which underscored just how opaque the process has been for lawmakers, including those, like Menendez, who hold some of the most powerful positions related to foreign policy on Capitol Hill. Among them: "Which agency has the lead for evacuation planning and implementation, and what is the State Department's role?"
Biden said last week that the administration had "already begun the process" of getting the Afghans out. But the administration's intention to relocate the Afghans to a third country while they wait for their visas is still being finalized after several weeks of an opaque process, and just days out from the US' withdrawal.
This story has been updated with comments from Biden on Friday morning and news that US troops have left Bagram Air Base
CNN's Kylie Atwood, Phil Mattingly, Barbara Starr and Katie Bo Williams contributed to this report.