US President Joe Biden says his country is on track to withdraw its military forces from Afghanistan by the end of August.

But Mr Biden added that he had spoken to military leaders so they would be prepared to “adjust that timetable, should that become necessary.”

“It is a tenuous situation,” he said from the White House on Wednesday morning (Australian time).

“The sooner we can finish the better. Each day of operations and brings added risk to our troops.”

Earlier, sharply divided leaders of the Group of Seven industrialised democracies had clashed over Mr Biden’s insistence on withdrawing from Afghanistan by August 31.

Mr Biden told the leaders that completing the mission depends on continued coordination with the Taliban, including continued access for evacuees to the airport.

In a partial show of unity, G7 leaders agreed on conditions for recognising and dealing with a future Taliban-led Afghan government.

But there was palpable disappointment Mr Biden could not be persuaded to extend the US operation at the Kabul airport to ensure that tens of thousands of Americans, Europeans, other third-country nationals and all at-risk Afghans can be evacuated.

The virtual meeting of the leaders of Britain, Canada, France, Germany, Italy, Japan and the US served not only as a bookend to the West’s 20-year involvement in Afghanistan that began as a response to the September 11, 2001 terrorist attacks but also a resigned acknowledgement from European powers that the US calls the shots.

“Our immediate priority is to ensure the safe evacuation of our citizens and those Afghans who have partnered with us and assisted our efforts over the past twenty years, and to ensure continuing safe passage out of Afghanistan,” the leaders said in a joint statement that did not address precisely how they would guarantee continuing safe passage without any military presence.

Going forward, the leaders said they would “judge the Afghan parties by their actions, not words”, echoing previous warnings to the Taliban not to revert to the strict Islamic form of government that they ran when they last held power from 1996 until the US-led invasion that ousted them in 2001.

“In particular, we reaffirm 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,” the leaders said.

“The legitimacy of any future government depends on the approach it now takes to uphold its international obligations and commitments to ensure a stable Afghanistan.”

Yet, individual leaders offered less sanguine descriptions of the meeting as well as the state of affairs in Afghanistan, which have dramatically changed since the bloc last met in Britain in June.

At the time of that summit, Afghanistan had been almost an afterthought with the leaders more concentrated on the coronavirus pandemic, China and Russia.

Although Mr Biden had announced his plan for complete withdrawal from Afghanistan, the Cornwall meeting did not anticipate Taliban’s rapid takeover.

“I want to stress again that of course the United States of America has the leadership here,” German Chancellor Angela Merkel said in Berlin after the meeting.

“Without the United States of America, for example, we – the others – cannot continue the evacuation mission.”

British Prime Minister Boris Johnson acknowledged he was unable to sway Mr Biden to extend the US military presence past the end of the month.

“You’ve heard what the president of the United States has had to say, you’ve heard what the Taliban have said,” he said.

A senior French official said President Emmanuel Macron had pushed for extending the August 31 deadline but “that’s in the hands of the Americans”.

On Monday, CIA chief William Burns met Taliban leader Mullah Abdul Ghani Baradar in Kabul in talks in which the Taliban underscored they would not accept a US military presence at the airport beyond August 31.

The White House noted that the risk of an attack from ISIS or other terrorist groups increased each day American troops stayed at the airport.