TEHRAN, Iran — Iran began a procession Monday through its capital, Tehran, for the funeral of the late Supreme Leader Ayatollah Ali Khamenei.

The 36-year rule of Khamenei built the Islamic Republic of Iran into a powerful anti-U.S. force.

Iran’s President Masoud Pezeshkian, Parliament speaker Mohammad Bagher Qalibaf — who has led the negotiations with the US — and Esmail Qaani, who leads the elite Quds Force of the paramilitary Revolut...