Iraq's electoral commission has ruled that the country's elections will go ahead as planned on 30 January.
Shia Muslim cleric Grand Ayatollah Ali Sistani backs a prompt vote
The interim government has also said it is determined that the vote for a national assembly will not be delayed.
Groups - representing mostly Sunni Muslims, Kurds and secular Iraqis - had asked for a six-month delay because of violence in some parts of the country.
Meanwhile, aid is being delivered to Falluja following the heavy US-led offensive on the city.
The Iraqi Red Crescent told the BBC it was delivering aid on a daily basis.
North of Baghdad, a US soldier was killed in a roadside bomb on Saturday, the US military said.
January's vote for a transitional assembly will lead to the writing of a constitution. Full elections for a new government are due by the end of 2005.
"Postponing the elections is out of the question," electoral commission chairman Abdel Hussein al-Hindawi told reporters. "As far as we are concerned, the elections will be held as scheduled by the fundamental law.
"In theory the elections cannot be postponed, bar a political disaster."
Several Sunni leaders have called for an election boycott
The US ambassador to Iraq, John Negroponte, said he believed there would be "adequate security" to allow elections to be held, AFP news agency.
Earlier, a spokesman for interim Iraqi Prime Minister Iyad Allawi said: "The government is determined to hold elections at the scheduled date and is working with the various political forces to that purpose."
The deadline of the end of January for elections is laid out in the temporary Iraqi constitution, and the date is also approved by the UN Security Council.
The electoral commission has put back the deadline for prospective electoral candidates to register from 22 November to 5 December in the provinces and 10 December in Baghdad.
Politicians from the country's Shia Muslim majority have come out strongly against delaying the vote.
In the Shia holy city of Najaf, a spokesman for the religious leaders, Mohammed Hussein al-Hakim, said any delay would be "unacceptable".
He said was speaking on behalf of four key leaders in Najaf, including Iraq's top Shia cleric, Grand Ayatollah Ali Sistani.
The politicians behind Friday's petition for a delay - representing 17 Iraqi groups - argued that clashes between US-led forces and insurgents in Sunni areas could keep many people from voting.
Some Sunni leaders have called for a boycott of the vote.
"It is unthinkable that a large and important section of Iraqi society be left out of the political process," said Adnan Pachachi, a senior secular politician at the head of the drive to postpone elections, on Saturday.
The Iraqi Red Crescent has told the BBC that aid is flowing into Falluja, nearly three weeks after the US-led offensive began there.
Convoys carrying food, water, medicine and blankets are now entering Falluja daily but there is still no running water or electricity.
A Red Crescent spokesman said thousands of families were in critical need of assistance, although no outbreaks of disease have been reported among the widespread destruction.