In the message to Angelo Bagnasco, who leads Italy's Bishops' Conference (CEI), the UCOII said: "We are relieved and immensely grateful for the position voiced by senior officials from the Italian Bishops' Conference in support of official places of worship for Muslims, an issue which nowadays has wrongly become a political hot potato."
"The brotherly solidarity of the great majority of Christians, which we have experienced at thousands of inter-faith gatherings and debates, has been strongly confirmed," the statement added.
Speaking to journalists on Tuesday during the CEI's general assembly at the Vatican, CEI secretary-general Mariano Crociata said the Catholic Church backed "the right to freedom of worship and places of worship to exercise this fundamental right".
"We must take account of the social needs of our communities as Italy's constitution requires," Crociata said.
Muslims were due on Wednesday to rally in Milan's central Piazza San Babila in support of the opposition centre-left's candidate for mayor Giuliano Pisapia who has voiced support for the building of a Milan mosque.
Pisapia will this weekend stand against conservative incumbent Letizia Moratti in an electoral run-off. In the first round of voting last week in which no candidate gained an outright majority of votes, Pisapia bested Moratti, taking some 48 percent of votes compared to her 42 percent.
The issue of an official mosque is a politically charged one in Milan which has been a conservative stronghold for almost two decades. Moratti, a former national education minister from the ruling People of Freedom Party says she opposes the construction of the mosque requested by Muslims.
Pisapia has criticised Moratti's position saying Milan should allow a proper place of worship for its Muslim community, which has been forced to hold prayers in makeshift venues such as garages and a disused cycle stadium.