When Leo III started making movements to ban the worship of icons in the 720s, the Pope in Rome, Gregory II, criticised it from the outset. Theophanes, a Byzantine iconophile writing in the early 9th century, says this about Gregory's feelings against the Roman church accepting iconoclasm:

Gregory the holy bishop of Rome repudiated [Patriarch] Anastasios … and reproved Leo by means of letters for the latter’s impiety.

Gregory went further to undermine Byzantine hegemony by calling a synod and only inviting western bishops. The Liber Pontificalis records Gregory's decree:

If anyone thenceforth… should remove, destroy, profane and blaspheme against this veneration of the sacred images… let him be driven forth from the body and blood of our Lord Jesus Christ.

At the Council of Hieria of 754, all 338 bishops of the Byzantine church agreed with iconoclasm, but the papacy and the eastern patriarchies of Antioch, Jerusalem, and Alexandria refused to send representatives, tacitly disagreeing with the movement.

In the 4 out of the 5 patriarchies of the Pentarchy, icons were clearly just too popular among the laity and clergy to be banned, so much so that the Pope was willing to undermine Byzantine authority to threaten the excommunication of iconoclasts. If the Byzantine church had not relented on iconoclasm in 787 then it is more than likely that the Papacy would have 'driven forth' any relationship with the Byzantine church, creating a schism between east and west patriarchies.