President Joe Biden told G7 leaders Tuesday the United States was "on pace" to complete its pullout from Afghanistan by August 31 but contingency plans were being drawn up in case the self-imposed deadline could not be met.
The White House said Biden also told Group of Seven leaders in a conference call that completing the US troop withdrawal from Afghanistan by the end of the month depends on "continued coordination" with the Taliban and access for evacuees to Kabul airport.
The United States has evacuated around 58,000 people, including more than 4,000 Americans, from Afghanistan since August 14, the day before the Taliban entered Kabul and took power, according to US officials.
Several thousand other people have been evacuated by allied European nations such as Germany and the United Kingdom.
The Taliban urged skilled Afghans not to flee the country on Tuesday and warned the United States and its NATO allies they would not accept an extension to the evacuation deadline.
A spokesman for the hardline Islamist group told America to stop taking "Afghan experts," such as engineers and doctors, out of the country.
"This country needs their expertise. They should not be taken to other countries," Taliban spokesman Zabihullah Mujahid told a press conference in the capital.
"They should not encourage the Afghan people to flee Afghanistan."
White House spokeswoman Jen Psaki said Biden had told G7 leaders the US mission in Kabul "will end based on the achievement of our objectives."
"He confirmed we are currently on pace to finish by August 31," Psaki told reporters.
"He also made clear that with each day of operations on the ground, we have added risk to our troops with increasing threats from ISIS-K," she said, adding that "completion of the mission by August 31 depends on continued coordination with the Taliban, including continued access for evacuees to the airport."
"The president has asked the Pentagon and the State Department for contingency plans to adjust the timeline should that become necessary," the White House spokeswoman said.
European nations have said they would not be able to airlift all at-risk Afghans before the August 31 cut-off, and Biden has faced calls from all corners to extend the evacuation window.
- 'It will not be enough' -
Mujahid, the Taliban spokesman, said the Islamist group opposes an extension.
"They have planes, they have the airport, they should get their citizens and contractors out of here," he said.
US-led troops have ramped up operations to get thousands of people out of Kabul by August 31 -- the deadline set by the US before the fall of the capital for all foreign troops to have pulled out.
Germany said Tuesday Western allies simply cannot fly out every Afghan who needs protection before the cut-off date.
"Even if (the evacuation) goes on until August 31 or even a few days longer, it will not be enough," Foreign Minister Heiko Maas told Bild TV.
Earlier, France said it would have to end evacuations from Kabul's airport on Thursday if the United States stuck to the deadline, and Spain said it would not be able to rescue all Afghans who served Spanish missions.
EU leaders at the G7 meeting urged Biden to continue to secure Kabul airport until operations to evacuate vulnerable Afghans are complete.
Many Afghans fear a repeat of the brutal interpretation of Islamic law that the Taliban implemented when first in power from 1996-2001, or retribution for working with the US-backed government over the past two decades.
On Tuesday, Mujahid said female Afghan government workers should stay home until security conditions in the country improve.
Dozens of Afghan schoolgirls, faculty and staff at the war-torn country's only boarding school for girls -- the privately run School of Leadership, Afghanistan -- will be evacuated to Rwanda, the institution's founder Shabana Basij-Rasikh said.
Days earlier, Basij-Rasikh said she was burning her students' educational records, in an effort "to protect them and their families."
Australia also has evacuated dozens of sportswomen and athletes under threat in the country, with Khalida Popal, the former national football team captain, saying some had been beaten as they fled.
- Secret meeting -
The Taliban achieved their stunning victory after Biden pulled out nearly all American troops from Afghanistan, following through on a deal struck with the movement by former president Donald Trump.
However, Biden was forced to redeploy thousands of troops after the fall of Kabul to oversee the airlift.
According to The Washington Post, US Central Intelligence Agency chief William Burns held a secret meeting in Kabul on Monday with Taliban co-founder Mullah Abdul Ghani Baradar, although no details were reported and neither the CIA nor the Taliban confirmed it.
The rush to leave Kabul has sparked harrowing scenes and left at least eight people dead.
Some have been crushed to death, and at least one, a youth football player, died after falling off a plane.
The Taliban have repeatedly claimed to be different from their 1990s incarnation, and have declared an amnesty for government forces and officials.
But an intelligence assessment conducted for the United Nations said militants were going door-to-door hunting former government officials and those who worked with US and NATO forces.
In the capital and other cities, the former insurgents have enforced some sense of calm, with their fighters patrolling the streets and manning checkpoints.