The United Nations' special adviser on sport for development and peace, Wilfried Lemke, has affirmed in a letter to FIFA that Israeli settlements are illegal under international law.
The opinion, requested by football's governing body as a row rages over Israeli football clubs based in West Bank settlements, was sent on October 7, ahead of a FIFA meeting this week where the issue is expected to be discussed.
The Palestinian Football Association, along with international campaigners, have demanded that six settlement-based teams either relocate to Israel's pre-1967 territory, or be banned.
In his letter, Lemke said the UN Security Council "has determined that Israeli settlements in occupied territory have no legal validity, as they are in breach of international law, and that such practices are an obstruction to achieving a comprehensive, just and lasting peace in the Middle East."
Lemke added: "all teams playing in recognised FIFA competitions should abide by the laws of the game", continuing: "I therefore urge a resolution of any disputes in line with the United Nations security council resolutions and FIFA statutes within a reasonable timeframe."
Meanwhile, Palestinian children marched on Israeli settlement Ma'ale Adumim to play football there on Tuesday, in a protest ahead of FIFA's meeting. Israeli occupation forces blocked their path before the entrance to the illegal settlement.
Last month, Human Rights Watch accused FIFA of "holding games on stolen land." By "sponsoring matches in Israeli settlements in the West Bank on land unlawfully taken from Palestinians", the group stated, FIFA is failing to "fulfil its human rights responsibilities."