The Leader’s address is set for 01:00 GMT (17:30 local time) to hundreds of thousands of mourners who have descended on Tehran, from all over Iran and other countries.
More than 300 foreign correspondents will be covering the event. Iran’s biggest airport, which is named after Imam Khomeini, will shut down for four hours from 16:00-20:00 hours local time while Ayatollah Khamenei delivers his speech.
Imam Khomeini passed away aged 86 at the night of June 3, 1989. Hailed as one of the most influential figures in modern history, he led popular protests against Iran's former Pahlavi regime which was a key ally of the United States.
Imam Khomeini spent many years in exile in Iraq, Turkey and France, from where he led a swelling grassroots movement which ultimately put an end to millennia of monarchical rule in Iran.
The headquarters marking the anniversary called on Iranians to attend the ceremony as “America is extremely isolated in the international scene and has confessed to the failure of its old plots, on the 40th anniversary of the Islamic Revolution in Iran.”
The anniversary is one day ahead of another landmark, June 5, 1963, the day Imam Khomeini’s first revolt against the monarchy witnessed demonstrations in Tehran and Qom.