"What we have seen in the last year is actually a huge setback and the tragedy for Afghanistan, but also for all those Allies and partners who worked so hard to create a more peaceful and democratic Afghanistan," Stoltenberg said during a press conference.
The Western countries managed to cope with terrorism in Afghanistan, but did not fulfill the much more ambitious task of building a free and democratic state, Stoltenberg added.
An interim Afghan government led by the Taliban came to power last fall after the withdrawal of US troops from the country and the collapse of the US-backed government.
The Taliban takeover triggered economic disarray and food shortages that have pushed the country to the brink of a humanitarian crisis. Thousands of Afghans have fled the country fearful of the Taliban, widespread violation of human rights, and the deprivation of women and girls of their freedoms.