President Barack Obama is endorsing the Palestinian demand for their future state to be based on the borders that existed before the 1967 Middle East war, in a move that will likely infuriate Israel.
Israel says the border of a Palestinian state has to be determined through negotiations.
In a speech outlining US policy in the Middle East and North Africa, Obama on Thursday sided with the Palestinian opening position, a day ahead of a visit to Washington by Israeli Prime Minister Benjamin Netanyahu.
Netanyahu is vehemently opposed to referring to the 1967 borders.
Until Thursday, the US position had been that the Palestinian goal of a state based on the 1967 borders, with agreed land swaps, should be reconciled with Israel's desire for a secure Jewish state through negotiations.