"The occupiers want to favour one party over the other," Sheikh Ahmed Abd al-Ghafur told worshippers on Friday at Baghdad's Umm al-Qura mosque, in reference to the Shia.
"The Iraqis want elections, that's important. But what's more important is to think about ending the occupation because if elections are held under occupation they will not be fair ..."
"What is the alternative? A timetable for the end of the occupation, a deployment of forces from the United Nations and the Arab League, the adoption of a constitution and then elections," he said.
"The Americans are not able to protect themselves, how can they protect the Iraqis? And elections cannot be valid in the absence of a constitution," Abd al-Ghafur said.
Iraq's top Shia cleric Grand Ayat Allah Ali al-Sistani is demanding a vote be held before a 30 June deadline for the handover of political power, so that an elected administration takes over from the occupation forces.
But the US-led occupation argues that free and fair elections cannot be held within the deadline. It proposes a selection process based on regional caucuses for the first post-occupation legislature.