The United Nations says replacing its Palestinian relief agency UNRWA in Gaza and the West Bank is not the world body's responsibility, signaling it was Israel's problem, according to a letter excerpt seen by Reuters.

The U.N. formally responded in a letter to Israel's decision to cut ties with the United Nations Relief and Works Agency, a move that UNRWA has said leaves its operations in Gaza and the West Bank at risk of collapse.

Under a new law, Israel told the U.N. on Sunday it was ending a 1967 cooperation agreement with UNRWA that covered its protection, movement and diplomatic immunity. The law will also ban UNRWA's operations in Israel from late January.