https://www.bbc.com-image caption The announcement means the US will miss a May deadline for a pullout agreed with the Taliban last year
US President Joe Biden is set to announce that American troops will leave Afghanistan by 11 September, officials have told US media.
The US would miss a May deadline for a pullout agreed with the Taliban by the Trump administration last year.
The new deadline would coincide with the 20th anniversary of the terror attacks on the World Trade Center and the Pentagon in the US in 2001.
Mr Biden had previously said the 1 May deadline would be tough to meet.
US and Nato officials have said the Taliban have so far failed to live up to commitments to reduce violence.
They have been warned that if they attack US troops during the pullout phase, they “will be met with a forceful response”, a senior administration official who was briefing reporters on the decision said.
Mr Biden is due to make the announcement himself on Wednesday.
The deal signed in February 2020 said the US and its Nato allies would withdraw all troops in 14 months if the Taliban upheld its promises, including not allowing al-Qaeda or other militants to operate in areas it controlled and proceeding with national peace talks.
Although the Taliban, a hardline Islamist movement, stopped attacks on international forces as part of the historic agreement, it has continued to fight the Afghan government.
There are fears that if foreign military forces withdraw before a lasting agreement is reached, the Taliban might seize power.
The US says it has some 2,500 troops still in Afghanistan.