An influential summit of Muslim countries has backed the Palestinians ahead of the United States' unveiling of a peace plan that is expected to dismiss their political aspirations.

Meeting in Mecca, the 57-country Organisation of Islamic Cooperation (OIC) denounced on Saturday the controversial US move to transfer its Israeli embassy to Jerusalem and urged its members to "boycott" those countries that have opened embassies in the disputed city, whose eastern part is regarded by Palestinians as the capital of their future state.

The OIC summit also reaffirmed its opposition to illegal Israeli measures aimed at changing facts in occupied Palestinian territories and refused to recognise Israel's sovereignty over the Golan Heights.

"The Palestinian people have the right to achieve their inalienable national rights, including their right to self-determination and the establishment of an independent and sovereign Palestinian State," the OIC said in a joint statement.

It came as Jared Kushner, Donald Trump's son-in-law, readies a long-awaited Middle East peace plan whose economic aspects are set to be rolled out at a conference in Bahrain later this month.

Dubbed the "deal of the century," the plan has already been rejected by the Palestinians, who expect it to be skewed in Israel's favour.

Speaking to the Reuters news agency on Friday, a senior Palestinian official said that "the plan doesn't give justice to the Palestinians".

"The Palestinian cause is being liquidated - no Jerusalem [as capital], no right of return for refugees, no sovereign state. That is why this American project is dangerous," the official said.

The plan has reportedly been thrown into disarray by the uncertainty over the future of key-US ally Israeli Prime Minister Benjamin Netanyahu, who was forced on Wednesday to call fresh elections after failing to form a government after April elections.

Kushner, who was in Jerusalem on Friday on the last leg of a regional tour aimed at selling the plan, had looked to an alliance with Saudi Arabia against Iran as a way to gain Arab support.

But Saudi King Salman told leaders of the OIC countries gathered at the summit: "The Palestinian cause is the cornerstone of the works of the Organisation of Islamic Cooperation, and is the focus of our attention until the brotherly Palestinian people get all their legitimate rights.

"We reaffirm our unequivocal rejection of any measures that would prejudice the historical and legal status of Quds [Jerusalem]."

Saudi Arabia last month said it would attend an economic conference in Bahrain that the US intends to be the jumping-off point for the "deal of the century".

The gulf kingdom also received backing amid escalating tensions with Iran, as King Salman warned against "terrorist" attacks in the region following alleged sabotage attacks on two Saudi oil tankers.

"We confirm that terrorist actions not only target the kingdom and the Gulf region, but also target the safety of navigation and world oil supplies," the king told Muslim leaders.

Iran's President Hassan Rouhani was not present at the conference, nor was Turkish President Recep Tayyip Erdogan.

The OIC comprises Muslim-majority countries and those with a sizeable Muslim population, such as Uganda and Guyana, and has a collective population of 1.9bn.