The chief US administrator for Iraq says the UN estimates that "technical problems" will prevent full elections taking place for at least a year.
Iraqi Shias had demanded full elections in the coming months
In an interview with an Arabic TV station, Paul Bremer pointed to a lack of democratic and legislative infrastructure in Iraq.
The country's Shia majority have called for direct polls instead of a phased transition planned by the coalition.
But a UN commission sent to Iraq found early elections were unfeasible.
The comments are the first from Mr Bremer about the timing of elections since the UN secretary-general declared that they could not take place before the planned handover of power on 30 June, says the BBC's Jonny Dymond in the Iraqi capital Baghdad.
Iraq lacked the infrastructure to allow elections before the US-imposed deadline for the handover of power to a provisional Iraqi authority, Mr Bremer told Dubai-based al-Arabiya TV on Friday.
"[Iraq] has no law governing political parties, it has no voters' list, it has not had a credible reliable census in almost 20 years, there are no constituent boundaries to decide where elections would take place," he said.
"These technical problems will take time to fix - the UN estimates between a year and 15 months. It might be that it could be sped up a little bit.
NOVEMBER POWER TRANSFER AGREEMENT
Feb 2004: Fundamental Law (provisional constitution) to be introduced
May, 2004: Selection of Transitional National Assembly (TNA)
June 2004: TNA to take power; Coalition Authority and Governing Council to dissolve
March 2005: Constitutional Convention elected to draft new constitution
Dec 2005: New constitution; elections and appointment of new government
"But there are real important technical problems why elections are not possible, as the secretary-general announced," he said.
In a timetable set out last November, the coalition envisaged elections only taking place by December 2005.
In the meantime, the coalition had planned to transfer power to a transitional authority of notables selected through unelected regional caucuses.
Large Shia protests called by Iraq's top Shia cleric, Grand Ayatollah Ali al-Husseini al-Sistani, demanded full direct elections before 30 June to choose a legislature.
But a UN team led by Lakhdar Brahimi found that would leave too little time to organised free and fair elections.
Mr Bremer reaffirmed the 30 June deadline last Thursday.