UN Secretary General Antonio Guterres has sent a letter to Israeli Prime Minister Benjamin Netanyahu protesting a new law that could effectively cripple the UN agency responsible for aiding Palestinian refugees (UNRWA), AFP reports.

The ban is due to start in three months.

In the letter, which was seen by AFP, Guterres said the law could have “devastating consequences” for Palestinians in Gaza and the West Bank because there is no reasonable alternative to UNRWA for providing the aid and assistance these people need.

“I appeal to you and to the government of Israel to prevent such devastating consequences and to allow UNRWA to continue carrying out its activities in the Occupied Palestinian Territory, including East Jerusalem, in accordance with its obligations under international law,” Guterres wrote.

Guterres argued that under international law an occupying power must implement mechanisms for aiding the people living in that occupied territory. “Israel, as the occupying power, continues to be required to ensure that the needs of the population are met,” Guterres wrote.

“If Israel is not in a position to meet such needs, it has an obligation to allow and facilitate the activities of the United Nations, including UNRWA, and other humanitarian agencies, until the needs of Palestine refugees in the Occupied Palestinian Territory are met,” he added.