The West Bank barrier Israel is building will be devastating for Palestinians if completed along its proposed route, the UN says.
In a report, the UN said thousands of Palestinians had already been cut off from their jobs, land or key services.
The report blamed Israel's decision to build the barrier inside the West Bank rather than along the agreed border.
The report was compiled to mark four years since an International Court of Justice ruling on the barrier.
In an advisory judgement rejected by Israel, the court ruled in 2004 that the barrier is illegal where it cuts into the West Bank.
Israel says the barrier is needed to keep out Palestinian attackers, but Palestinian officials describe the barrier's route as a land-grab.
Major impact
Detailing what it called the humanitarian impact of the barrier, the UN report said some Palestinian communities which did export food before had now been reduced to receiving food aid.
It focused on agricultural areas close to the city of Qalqilya, which is enclosed by the barrier on three sides, and where other farmers and families are forced to live between two sections of the barrier.
Almost 60% of the barrier had now been built, the report said, asserting that thousands more Palestinians would suffer if construction continued.
"The majority of the route, approximately 87%, runs inside the West Bank and East Jerusalem, rather than along the 1949 Armistice Line (Green Line)," the report said.
"This has a major impact on Palestinian villages, towns and cities, isolating communities and separating tens of thousands of people from services, lands and livelihoods."
It described the "restrictive" permits policy in place along the completed northern section of the route, and said some areas now faced increased unemployment, "displaced" young men, and worsening economic conditions.
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