Joe Biden on Thursday said that the US military mission in Afghanistan will end on August 31, defending his decision to withdraw American troops after more than 20 years of fighting despite the threat of a resurgent Taliban.

“I will not send another generation of Americans to war in Afghanistan with no reasonable expectation of achieving a different outcome,” the president said while speaking from the White House.

Biden said the country had completed its objectives of finding Osama bin Laden, the al-Qaeda leader and mastermind of the September 11 2001 attacks, and had weakened the terrorist threat to the US mainland from Afghanistan.

“That’s why we went. We did not go to Afghanistan to nation-build,” he said.

It would now fall to the Afghan people to “decide their future” and “how they want to run their country”, he said, but the prospect of keeping US troops there for “just one more year”, as some of his critics have urged him to do, was “not a solution”.

Biden’s comments come a week after the US withdrew from its main military base in Afghanistan, even as a resurgent Taliban has gained territory.

The Taliban has launched numerous offensives against Afghan forces and civilians, while peace talks between the Taliban and the Afghan government that began in September 2020 have failed to produce a political settlement or ceasefire.

General Austin Miller, the US military commander in Afghanistan, warned the country could descend into a worsening civil war during a press conference last week.

Eighty out of Afghanistan’s approximately 400 districts had fallen to Taliban control since May, said Mir Haider Afzaly, an MP and chair of the Afghan parliament’s defence commission.

Biden on Thursday denied that US intelligence agencies had forecast the imminent fall of the Afghan government. “The Afghan government has to come together, they clearly have the capacity to sustain the government in place,” he said, referring to forces and military equipment. “The question is will they generate the kind of cohesion to do it?”

He later added that the likelihood of “one unified government . . . controlling the whole country” was “highly unlikely”.

“Never has Afghanistan been a united country, not in all of its history,” Biden said.

The president, along with his vice-president Kamala Harris, was briefed on the progress of the US’s military drawdown from Afghanistan by the administration’s national security team on Thursday morning.

The Afghan military is set to take over Bagram Airfield, the vast base that was once the centre of its nationwide command in the country, following the withdrawal of a majority of US troops.

Biden pledged again that any Afghan nationals who had worked alongside US forces would be eligible for “dramatically accelerated” entry to the US.

Earlier on Thursday, Jen Psaki, White House press secretary, said the US was “not having a mission accomplished moment”.

“It is a 20-year war that has not been won militarily,” she said.

Additional reporting by Lauren Fedor