Iranian Supreme Leader Ali Khamenei criticized the US plan for peace in the Middle East as a "betrayal of the Islamic nation", calling on the Gulf states not to support it.

"The goal of this conference is to achieve the American plan of treachery called the Deal of the Century," Khamenei said in a sermon on Eid al-Fitr. He added that this deal "will not materialize, and this deal is a betrayal of the Islamic nation will not see the light."

He added that "the leaders of some Islamic countries are paving the ground for the implementation of the deal of the century," asserting that "the betrayal of some Islamic countries of the Palestinian cause requires attention."

"The rulers of Saudi Arabia and Bahrain should know that they have entered an endless swamp."

In remarks published on his official website on Wednesday, Khamenei stressed that the Islamic Republic does not seek to "throw the Jews into the sea," and felt that a referendum is the solution to the Palestinian-Israeli conflict.

He reiterated Iran's proposal to hold a vote in which the "Muslim, Christian and Jewish residents of Palestine, as well as the Palestinian refugees," would participate in the government system.

The Palestinians rejected the plan, led by US President Donald Trump's Jared Kouchner, and say the White House policies are clearly biased toward Israel.

The United States will unveil the economic aspects of the plan at a conference in Manama on June 25, but said the political plan will only be put "when the time is right."

International financial institutions, including the International Monetary Fund (IMF) and the World Bank, will participate in the Bahrain conference.

A representative of the Fund said that the latter "received an invitation to attend the conference, and expected to attend other international financial institutions."

The European Bank for Reconstruction and Development (EBRD) confirmed that there would be "its own representative," while a World Bank spokesman said he had received an invitation "and is expected to attend."

The United Nations announced last Thursday that it would not participate in the conference.