Iran's supreme leader has said Saudi Arabia's alignment with the United States and Israel is "certainly a betrayal" of the Muslims.

Ayatollah Ali Khamenei made the remark at a conference attended by parliamentary representatives from Islamic countries on Tuesday in Tehran, according to a statement published on his official website.

Discussing the recent US recognition of Jerusalem as the capital of Israel, he said the Holy City was "undoubtedly" the capital of Palestine, adding that Washington's move "won't bear results".

According to the statement, Khamenei also accused Saudi Arabia of helping the US and the "Zionists".

"This is certainly a betrayal of the Islamic Ummah and the Muslim World," he said.

In another part of his speech, he said: "We're ready to act brotherly even with those among the Muslims who were once openly hostile to Iran.

"The world of Islam, with such a large population and plenty of facilities, can certainly create a great power within the world and become influential through unity.

"Such warmongering among the world of Islam must be stopped and we should not allow that a safe haven be created for the Zionist regime."

Regional rivals

Iran, the leading Shia Muslim power, and Sunni Muslim Saudi Arabia, a key US ally, are rivals for influence in the Middle East where they support opposing sides in Yemen, Syria, Iraq and Lebanon.

US President Donald Trump said on a visit to Jerusalem last year that a shared concern about Iran was driving many Arab states closer to Israel.

An Israeli cabinet minister said in November that Israel had covert contacts with Saudi Arabia amid common concerns over Iran.

Iran does not recognise the state of Israel.