President Joe Biden and other top US officials were stunned by the pace of the Taliban’s nearly complete takeover of Afghanistan as the planned withdrawal of American forces urgently became a mission to ensure a safe evacuation.

The speed of the Afghan government’s collapse and the ensuing chaos posed the most serious test of Mr Biden as commander in chief, and he was the subject of withering criticism from Republicans who said that he had failed.

Mr Biden campaigned as a seasoned expert in international relations and has spent months downplaying the prospect of an ascendant Taliban while arguing that Americans of all political persuasions have tired of a 20-year war, a conflict that demonstrated the limits of money and military might to force a Western-style democracy on a society not ready or willing to embrace it.

By Sunday, though, leading figures in the administration acknowledged they were caught off guard with the utter speed of the collapse of Afghan security forces.

The challenge of that effort became clear after reports of sporadic gunfire at the Kabul airport prompted Americans to shelter as they awaited flights to safety.

“We’ve seen that that force has been unable to defend the country, and that has happened more quickly than we anticipated,” US secretary of state Antony Blinken told CNN, referring to the Afghan military.

The turmoil in Afghanistan resets the focus in an unwelcome way for a president who has largely focused on a domestic agenda that includes emerging from the pandemic, winning congressional approval for trillions of dollars in infrastructure spending and protecting voting rights.

Mr Biden remained at Camp David on Sunday, receiving regular briefings on Afghanistan and holding secure video conference calls with members of his national security team, according to senior White House officials.

The next several days could be critical in determining whether the US is able to regain some level of control over the situation.

Discussions were under way for Mr Biden to speak publicly, according to two senior administration officials who requested anonymity to discuss internal conversations.

Mr Biden, who is scheduled to remain at Camp David through to Wednesday, is expected to return to the White House if he decides to deliver an address.

Mr Biden is the fourth US president to confront challenges in Afghanistan and has insisted he would not hand America’s longest war to his successor.

But the president will likely have to explain how security in Afghanistan unravelled so quickly, especially since he and others in the administration have insisted it would not happen.

“The jury is still out, but the likelihood there’s going to be the Taliban overrunning everything and owning the whole country is highly unlikely,” Mr Biden said on July 8.

As recently as last week, Mr Biden publicly expressed hope that Afghan forces could develop the will to defend their country.

But privately, administration officials warned that the military was crumbling, prompting Mr Biden on Thursday to order thousands of American troops into the region to speed up evacuation plans.

One official said Mr Biden was more sanguine on projections for the Afghan fighters to hold off the Taliban in part to prevent a further erosion in morale among their force.

It was ultimately for naught.

Presidents Barack Obama and Donald Trump also yearned to leave Afghanistan, but ultimately stood down in the face of resistance from military leaders and other political concerns.

Mr Biden, on the other hand, has been steadfast in his refusal to change the August 31 deadline, in part because of his belief that the American public is on his side.

A late July ABC News/Ipsos poll, for instance, showed 55% of Americans approving of Mr Biden’s handling of the troop withdrawal.

Most Republicans have not pushed Mr Biden to keep troops in Afghanistan over the long term and they also supported Mr Trump’s own push to exit the country.

Still, some in the party are stepping up their critique of Mr Biden’s withdrawal strategy and said images from Sunday of American helicopters circling the US Embassy in Kabul evoked the humiliating departure of US personnel from Vietnam.

Senate Republican leader Mitch McConnell deemed the scenes of withdrawal as “the embarrassment of a superpower laid low”.

Meanwhile, US officials are increasingly concerned about the potential for the rise in terrorist threats against the US as the situation in Afghanistan devolves, according to a person familiar with the matter who requested anonymity to discuss a sensitive security matter.