The US President has said that the American-led airlift from Afghanistan has to finish soon because of the increasing threat from the so-called Islamic State group's Afghan arm.
The longer the US stays in the country, Joe Biden said, there is an "acute and growing risk of an attack by a terrorist group known as ISIS-K," or Islamic State-Khorasan.
"Every day we're on the ground is another day we know that ISIS-K is seeking to target the airport and attack both US and allied forces," he added.
He was speaking at the White House after a virtual meeting of the G7 on the situation in Afghanistan.
The British Prime Minister said the group agreed that the Taliban must "guarantee" safe passage for those fleeing the country beyond the current 31 August evacuation deadline.
Boris Johnson, who convened the emergency meeting, said that he and his colleagues had approved "a road map for the way in which we're going to engage with the Taliban" in the future.
But he added that the "number one condition" was "to guarantee ... through August 31 and beyond, a safe passage for those who want to come out".
The UK chaired the talks among the group of wealthy countries, saying it would urge President Biden to extend his 31 August deadline to pull American forces out of Afghanistan.
The European Union also called on Mr Biden to continue to secure Kabul airport until operations to evacuate vulnerable Afghans were complete.
President of the European Council Charles Michel said European leaders had urged their "American friends" to "secure the airport as long as necessary to complete the operations and ensure a fair and equitable access to the airport for all nationals entitled to evacuation".
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However, Mr Biden told G7 leaders that the US is on course to complete its pull-out from Afghanistan by 31 August depending on cooperation from the Taliban, according to a White House statement.
The Pentagon made the recommendation that Mr Biden stick to his target date yesterday, US officials said.
"During a meeting this morning with the G7 leaders, the president conveyed that our mission in Kabul will end based on the achievement of our objectives. He confirmed we are currently on pace to finish by August 31st," White House spokesperson Jen Psaki said.
President Biden told the other G7 leaders that completing the mission "depends on continued cooperation from the Taliban, and told them of mounting concerns about increasing threats on the ground," she said.
"In addition, the president has asked the Pentagon and the State Department for contingency plans to adjust the timeline should that become necessary," Ms Psaki said.
Statement from @WhiteHouse on today's G7 meeting: @JoeBiden told leaders that the US is "currently on pace to finish by August 31st" but he has also asked Pentagon & State Department for contingency plans to adjust the timeline should that become necessary. #Afghanistan @rtenews pic.twitter.com/qLOoQmvNVy— Brian O'Donovan (@BrianOD_News) August 24, 2021
Earlier, UK Defence Secretary Ben Wallace said it was "unlikely" that evacuations from Afghanistan would be extended beyond 31 August.
A Taliban spokesman warned yesterday that the group would not agree to any extension, calling the issue a "red line", with any delay viewed as "extending occupation".
"If the US or UK were to seek additional time to continue evacuations - the answer is no. Or there would be consequences," Taliban spokesman Suhail Shaheen told Sky News.
The UK has continued to evacuate Western citizens and some Afghans from Kabul, with Mr Wallace warning the security situation was getting "more and more dangerous" as 31 August approaches.
The defence ministry said 8,458 people have been evacuated by the UK since 13 August, with nine military flights leaving Kabul in the last 24 hours.
More than half - 5,171 - are Afghans eligible to relocate to the UK under its programme to protect those who aided its military and civilian officials during their two-decade involvement in Afghanistan.
An individual on the UK's no-fly anti-terrorism watch list arrived as part of the evacuation, the interior ministry confirmed.
A spokesman said the individual was identified "as part of the rigorous checks process" and that after further investigation was deemed "not a person of interest to the security agencies or law enforcement".
Meanwhile, the US has evacuated "more than 4,000 American passport holders plus their families" from Afghanistan since mid-August, a senior State Department official has said.
"We expect that number to continue to grow in the coming days," the official told AFP.
"We are continuing to contact the Americans who have previously registered with Kabul embassy to determine whether or not they are still in Afghanistan, and to help them evacuate if they want to leave."
At the weekend, the US military said 2,500 Americans had been evacuated.
The G7 leaders also agreed that the Taliban will be "held accountable for their actions on preventing terrorism, on human rights in particular those of women, girls and minorities and on pursuing an inclusive political settlement in Afghanistan", according to a statement issued by Mr Johnson's Downing Street office.
The UK chairs the G7, which also comprises Canada, France, Germany, Italy, Japan and the United States.
Taliban warns against extension to airlift deadline
A Taliban spokesman has said the US should stop evacuating skilled Afghans, and warned Western forces against extending the 31 August deadline for airlifts out of the country.
The group said Americans were taking "Afghan experts" such as engineers out of Afghanistan.
"We ask them to stop this process," spokesman Zabihullah Mujahid said at a press conference in Kabul.
He also said the crowds of Afghans thronging Kabul airport seeking a flight out of the country could go home.
"We guarantee their security," he told the news conference.
Mr Mujahid also said there was no list of people targeted for reprisals.
"We have forgotten everything in the past," he said.
Meanwhile, the EU has moved all of its staff from Afghanistan, apart from some officials still working at Kabul airport, a spokesperson for the European Commission said.
"All the staff who needed to be evacuated have been evacuated," he told journalists in Brussels.
"We still have a core presence at the airport in order to manage what needs to managed, but the staff of the EU delegation and their families have all been evacuated."
Widespread chaos punctuated by sporadic violence has gripped Kabul's airport since the Taliban took over the Afghan capital on 15 August, with Western and Afghan forces driving back crowds desperate to flee.
Evacuations were being conducted on a "war footing" as foreign forces try to meet the 31 August deadline, a NATO diplomat said.
Thousands of Afghans have returned to their homes after learning that situation is "relatively calm" in provinces across the country, said the diplomat, who asked not to be identified, while cautioning that scant intelligence and security reports were coming in from remote districts.
Many Afghans fear reprisals and a return to a harsh version of Islamic law that the Taliban enforced while in power from 1996 to 2001, and there have been isolated, but numerous incidents posted on social media that have fanned those fears.
The Irish Government is sending military special forces to Afghanistan to help facilitate the evacuation of remaining Irish citizens.
A small group of Army Rangers and two Department of Foreign Affairs officials left for Kabul last night.
US media has reported that President Biden sent the head of the CIA to meet the Taliban's leader yesterday in the highest level diplomatic encounter since the militant group took over the Afghan capital.
The Washington Post, citing US officials who spoke on condition of anonymity, said CIA Director William Burns met Abdul Ghani Baradar in Kabul.
NBC News also reported that the men met, citing a senior diplomat in the region and another source familiar with the matter. Fox News also reported the meeting, citing on unnamed US official
France detains Afghan evacuee in Taliban inquiry - government
France has detained an Afghan it helped to transport out of the country as part of an investigation into links with the Taliban, according to a government spokesman.
The man is believed to be close to another Afghan evacuee who is suspected of working for the Taliban, Gabriel Attal told BFM-TV.
Both had been placed under surveillance on their arrival in France, and the man held was detained for violating the terms of this control measure.
Interior Minister Gerald Darmanin told France Info radio that he had left an area he was required to stay in for a "few minutes," insisting there had been no security lapse.
Mr Attal said the main suspect helped in the evacuation of French people from Afghanistan "at an incredibly tense moment and probably saved lives". But he had "links with the Taliban, at some point, and this needs to be specified".
According to a ministerial document seen by AFP, he admitted his membership of the Taliban and said he had worked as the armed head of a Taliban checkpoint in Kabul.