United States President Joe Biden is set to announce that American troops will leave Afghanistan by 11 September this year.
The US would miss a May deadline for a pull-out 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.
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.
The Taliban have been warned that if they attack US troops during the pull-out phase, they will be met with a forceful response.