The UN Security Council has voted to withdraw a UN force from Chad and the Central African Republic.
The 4,375-strong force is to pull out in stages by the end of 2010.
It was deployed in 2009 to protect hundreds of thousands of displaced Chadians and refugees from the Sudanese province of Darfur.
The withdrawal was requested by Chad. But Amnesty International warned that the UN decision could endanger thousands of refugees in the region.
"The Security Council should stand up for the vulnerable women, men and young people living in the region," Amnesty said before the vote.
"It is wholly unacceptable that this resolution is taking place before the Chadian government has shown it has a concrete plan to provide security."
On Tuesday, the 15-member Security Council decided unanimously to withdraw the force (Minurcat).
About one-third will begin leaving in July, and the final pullout is to commence in October.
The resolution calls on UN Secretary General Ban Ki-moon "to complete the withdrawal of all uniformed and civilian Minurcat components, other than those required for the mission's liquidation, by 31 December 2010".
The mission currently has 3,300 military and 1,075 civilian personnel in Chad and the Central African Republic.
Chadian President Idriss Deby said earlier this year that the force was no longer necessary, describing it as a failure.
Attempts to persuade Mr Deby change his mind have been unsuccessful, the BBC's Jonny Hogg reports.
The decision to withdraw does come at a time of thawing relations between Chad and Sudan - previously a major source of conflict in the region, our correspondent adds.
However, UN humanitarian agencies will stay in the region, trying to deal not only with the effects of conflict, but a growing hunger crisis.
Chad is home to 260,000 refugees from Sudan's war-torn Darfur region.