"The United Nations urges those participating in all peace efforts to consider the millions of ordinary Afghans, especially the victims of the conflict, who want a chance to live in peace so they can rebuild their lives."
The grim milestone also comes days after officials announced preliminary results in Afghanistan's latest presidential elections that put President Ashraf Ghani on track to secure a second term.
The Taliban have long viewed Ghani as an American stooge and have refused to negotiate with him, leading many to fear that fighting will continue even if the US secures an eventual deal with the militants.
Earlier this year, the UN reported that an "unprecedented" number of civilians had been killed or wounded in Afghanistan from July 1 to September 30 this year, saying there had been 1,174 deaths and 3,139 injuries in that period. A UN tally found that last year was the deadliest on record, with at least 3,804 civilian deaths caused by the war - including 927 children.