A week into the evacuation from Kabul, the US military was forced to take a drastic step: stop all flights from Hamid Karzai International Airport for seven hours because there was nowhere for the evacuees to go.

For months, military officials had urged the US State Department to convince other countries to take Afghans at risk from Taliban retaliation. They had largely failed to secure agreements with other countries, prompting officials across the US government to rush to try to find space for the evacuees.

The Biden administration's scramble was emblematic of failures over the past month, which culminated with a hastily organised airlift that left thousands of US-allied Afghans behind and was punctuated by a suicide bombing outside Kabul's airport that killed 13 US troops and scores of Afghans.

The chaotic end to America's longest war has sparked the biggest crisis of President Joe Biden's seven months in the White House, finger-pointing within the administration and questions about who, if anyone, would be held responsible.

Despite the missteps, the administration carried out one of the largest airlifts in history, evacuating more than 120,000 Americans, Afghans and people of other nationalities amid the threat of attacks by the militant Islamic State group.

The last US troops left Afghanistan on Monday.

Current and former officials and lawmakers said there is little appetite for Biden to fire or demote top advisers over the handling of the US withdrawal. The Democratic president, meanwhile, has strongly defended his administration's actions.

Frustrated and angry officials at the Pentagon have privately blamed the lack of urgency leading up to the airlift on the State and Homeland Security departments, who in turn have blamed the White House for slow decision-making.

"Finger-pointing is an ugly Washington sport ... in this case, fingers could be pointed in all directions and probably be right in each case," said Dan Fried, a former senior US diplomat now at the Atlantic Council think tank.

"A failure like this is collective. Everybody screwed up," Fried added.

A source familiar with the matter defended the evacuation planning and said the State Department was unaware of any concerns at the Department of Defense about a lack of urgency in the effort.

White House officials told Reuters that firings have not been discussed, but the administration expects Congress to aggressively investigate the turbulent exit from Afghanistan in hearings.

One Biden administration official, speaking on condition of anonymity, said any dismissal would be seen as a tacit admission that the president had erred in removing troops unconditionally from the South Asian nation.

Biden, in a defiant speech on Tuesday, defended his decision to withdraw the troops and stood by the evacuation plan.

"Some say we should have started mass evacuations sooner and 'Couldn’t this have be done — have been done in a more orderly manner?' I respectfully disagree," said Biden, who noted that he was ultimately responsible for the withdrawal.

Political decision

Biden's party narrowly controls the US Senate and House of Representatives, and aides in both chambers said that, while Democrats would investigate and expect to hold hearings, they are wary of giving Republicans a platform to attack the president.

Democratic congressional committee leaders have pledged thorough reviews of the events in Afghanistan, but they made clear they intend to look into the entire 20-year conflict, which unfolded under the watch of four presidents, starting with Republican President George W. Bush.

On Tuesday, White House spokeswoman Jen Psaki said the administration has provided many classified and unclassified briefings to lawmakers.

"Now, it's a 20-year war, so there's obviously a lot to dig into," she said.

Democrats want to pursue Biden's domestic agenda — expanding social programs, funding infrastructure and protecting voting rights. On the national security front, they want to highlight their investigation of the Jan 6 attack on the US Capitol by supporters of then-President Donald Trump.

How Congress eventually proceeds will depend on the level of interest from voters.

Less than 40 per cent of Americans approve of Biden's handling of the military withdrawal from Afghanistan, according to a Reuters/Ipsos poll released on Monday.

National security adviser Jake Sullivan said last month that the Biden administration would conduct a "hotwash" — an after-action review — to discover what went wrong in Afghanistan and that he expected results of that review to be made public.

White House officials said on Tuesday the review had not begun.

Who to blame?

The last month in Afghanistan was a series of failures, from the intelligence and military to diplomatic and immigration fronts, with one core error the failure to anticipate the speed of the Taliban's advance and collapse of the Afghan military.

"In some way, everyone is to blame," a US official said on condition of anonymity.

Some Republicans have pointed fingers at Sullivan and Secretary of State Antony Blinken as the ones most responsible for setting the conditions for a chaotic evacuation and have demanded their departure.

Republicans also have called for Biden to fire the US special envoy for Afghanistan, Zalmay Khalilzad, who negotiated the Trump administration's 2020 deal with the Taliban that set the stage for the withdrawal.

But when House Minority Leader Kevin McCarthy was asked whether he thought Biden or Blinken should be impeached, the California Republican did not answer, saying instead his focus was on getting the Americans out of Afghanistan.

Defense officials told Reuters the State Department appeared out of touch with the reality on the ground in Afghanistan and had too much confidence in the Afghan government.

During a congressional hearing in June, Blinken was asked if the administration was considering getting at-risk Afghans out of the country while their cases were being reviewed.

"If there is a significant deterioration in security, that could well happen, we discussed this before, I don't think it's going to be something that happens from a Friday to a Monday," Blinken said.

The Taliban seized two of Afghanistan's three largest cities — Kandahar and Herat — on Aug 13 and took Kabul, the capital, two days later.