The UN Security Council has agreed to a major reduction of peacekeepers in Sudan's Darfur region after US pressure led to a $600m cut in the UN budget for peace operations.

The council on Thursday unanimously adopted a resolution drafted by the UK that will cut the number of troops and police serving in the joint African Union-UN mission known as UNAMID by at least 30 percent.

Fears over UN's Darfur peacekeeping cuts

Al Jazeera's Hiba Morgan, reporting from Sudan's capital Khartoum, said the mission would be downsized in only 11 out of 36 stations of Darfur.

"UN plans to focus more on development for about 2.7 million displaced people in Darfur as opposed to protecting peace, which they think is no longer needed," she said.

Deployed in 2007, UNAMID has about 16,000 blue helmets on the ground who are tasked with protecting civilians in the war that Sudan's government forces and pro-Khartoum fighters are waging against rebel groups.

The drawdown will be gradual, carried out in two phases of six months.

A first drawdown will reduce the number of UNAMID troops from 13,000 to about 11,400 in six months before dropping to 8,735 by the end of June 2018.

The number of police will drop from 3,150 to 2,888 by January and 2,500 by June.

The smaller UNAMID will be redeployed to the region of Jebel Marra, where most of the recent violence has been reported.

The drawdown, however, could be reviewed if the Sudanese government fails to ensure protection in those areas from where the peacekeepers will withdraw.

UN Secretary-General Antonio Guterres will report to the council after six months on whether "conditions on the ground remain conducive to further reductions".

The costliest UN mission

The UN and the African Union maintain that the Darfur conflict is winding down and that the mission - among the costliest with a budget of more than $1bn - should be trimmed.

Human rights groups warn that the conflict is far from over and that the withdrawal of UN peacekeepers will leave many areas of the vast Darfur region without international witnesses.

"We recognise that the situation in Darfur remains fragile," said British Deputy Ambassador Peter Wilson.

"Nevertheless, we cannot shy away from the fact that the situation has evolved and it is right that UNAMID is adapted to reflect the current reality," Wilson told the council after the vote.

"We will not be taking our eyes off Darfur," he added.

The General Assembly is scheduled to vote on Friday on the new peacekeeping budget of $7.3bn, down from the current $7.87bn.

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Source: Al Jazeera and news agencies