The office of Rome's chief rabbi said the visit, scheduled for Wednesday, was off but gave no immediate details.
Italian media reports said the imam had been told not to go to the synagogue by Sunni religious leaders in Egypt because of opposition to Israel's blockade in the Gaza Strip.
Leading newspapers, quoting Islamic sources, said the imam, Ala Eldin al Ghobashy, had been contacted by al-Azhar University, Egypt's major centre of Sunni Islamic learning.
An official at the mosque told La Repubblica newspaper the meeting had been "postponed", and not cancelled. It also quoted unnamed officials at the mosque as saying "logistical reasons" lay behind the last-minute decision.
Rome's chief rabbi paid a landmark visit in 2006 to the sprawling mosque on Rome's outskirts.
It was the first by a chief rabbi of Rome since it opened in 1995 -- a gesture that had been expected to be reciprocated by the imam's visit.
Source: Reuters (English)