Tehran Friday prayer leader Ahmad Khatami called US President Donald Trump "stupid, arrogant and narcissistic" and warned ", if you hit one, you will take 10", on September 25 in his latest fiery speech as Iranian officials continue to negotiate indirectly with US counterparts in New York.

The hardline cleric praised President Masoud Pezeshkian's address to the UN General Assembly two days earlier as a "translation of death to America and death to Israel". That puts one of the establishment's loudest voices behind the reformist president's mix of openness to talks and threats of retaliation.

Khatami's comments come as US envoys hold talks with Foreign Minister Abbas Araghchi. Khatami used the same sermon to set domestic limits on the hijab and key state appointments, and has a record of incendiary Friday rhetoric against Trump.

"Despite Trump's lies, the ground, air and naval forces of the Islamic Republic of Iran are active," Khatami told worshippers at Tehran University. He said the armed forces had not neglected missile production "for a moment" during the ceasefire, and that fear of Iran's missiles had halted Israel.

He described Trump as "the most hated president in American history" and said "not one word" of the UN speeches by Trump and Israel's prime minister had been true. He said 12 US bases in the region had been damaged.

Khatami said Pezeshkian's speech was "logical, epic and brave" and had turned the UN into "a court against America and the Zionist regime".

He threatened people spreading rumours on social media, saying "we will make them miserable" if they did not stop.

On national unity, Khatami said the supreme leader was its "axis". He said key posts should not go to "Westernised" figures. He warned that "mocking the hijab breaks unity" and that officials should not speak in a way that made unveiled women feel "the system supports them".

Moving on to another subject, he called unveiled women citizens and welcomed their attendance at rallies, while hijab enforcement remains a flashpoint between hardliners and the Pezeshkian government which has eased off. 

Iranian officials have been cautious in recent months to incite further riots caused by religious police which has urked religious officials close to the Khatami camp.

Marking the new school year, Khatami said about 50 teachers and about 300 students had been killed in recent attacks.

Hardline Khatami is a member of the Assembly of Experts, the clerical body that appoints the supreme leader, and one of Tehran's rotating Friday prayer leaders. What he says is usually a reflection of the home of the supreme leader Mojtaba Khatami.