Nato faces “hard decisions” in 2021 over ending its two-decade presence in Afghanistan, Secretary General Jens Stoltenberg said.
Almost 2,000 US troops were withdrawn from the country last month.
Fewer than 12,000 soldiers from Nato countries remain in Afghanistan, mainly as trainers and advisers, but fears are rising that an unco-ordinated withdrawal could jeopardise stability.
Peace talks between the Taliban, which has demanded the withdrawal of Nato forces, and the Afghan government remain delicately poised, while violence persists across the country.
“As we continue to assess the situation in Afghanistan, it is clear that we will face a turning point early next year," Mr Stoltenberg said after an online meeting of Nato foreign ministers.
"If we stay, we risk continued fighting and an even longer-term engagement.
“If we leave, we risk Afghanistan once again becoming a safe haven for international terrorists and the loss of the gains made with such sacrifice.
"So there is a price for staying longer but there is also a price for leaving too soon.
“We will have to take some hard decisions when Nato defence ministers meet next February.
"But whatever we decide, we must do it in a co-ordinated and orderly way."
There has been a surge in violence in Afghanistan this year with often unrelenting Taliban attacks on the country’s beleaguered security forces and the added threat of an ISIS presence.
The already disastrous humanitarian situation has been worsened by the Covid-19 pandemic.
About $12 billion in aid was pledged over the next four years at a conference last month, but much of it is tied to the progress of the peace talks.
German Foreign Minister Heiko Maas was also cautious about withdrawing too soon and said clear conditions must be set if there were to be further troop reductions.
"To safeguard what we have reached so far, we must not take any rash actions," Mr Maas said.
"This is why we call on the alliance to have a very close look at how far the conditions for a further withdrawal have been met to avoid sending a wrong message regarding the peace process."