Iraq's parliament has approved last-minute changes to the draft constitution aimed at overcoming Sunni Arab objections.
Some Sunni leaders have called for a boycott of the referendum
The changes - agreed by representatives of the communities on Tuesday night - were endorsed without voting.
One Sunni party has said it will back the draft if MPs elected in the December elections can review it. Other Sunnis maintain their boycott.
On Saturday, Iraqis go to the polls to vote on the new constitution.
SUNNI CHARTER OBJECTIONS
Federalism, and forming of semi-autonomous regions
Terminology used to eradicate influence of former Baath regime
Structure of authority between presidency, parliament and government
At the end of the year, a committee will get together to have another look at the text of the constitution.
But the political deal-making is unlikely to bring a swift end to Iraq's long-running era of violence, the BBC's James Reynolds reports from Baghdad.
Attacks by insurgents continued on Wednesday when at least 30 people - mostly recruits looking for work - were killed by a suicide bomber in the northern town of Talafar.
It was the second major attack on the town in as many days. Up to 30 people were killed in Tuesday's attack on a crowded marketplace.
Parliament met to discuss the changes agreed by Sunni, Shia and Kurdish leaders during the three-day talks.
The proposed changes were read out by Humam Hamoudi, chairman of the committee charged with drafting the constitution.
"Since there was no objection after the reading of the modifications, we can consider it approved," he said.
Among the key additions to the 139-article draft constitution are:
- Article 1 that reads: "This constitution is a guarantee for the unity of Iraq."
- Article 4 that reads: "The federal and official organisations in the Kurdistan region use the Arabic language and the Kurdish language as the official languages."
- Article 131 that reads: "Just being a member of the Baath Party is not grounds for prosecution and any [former] member is treated equally before the law and has all protections of the law."
"There is no excuse for Arab Sunnis to boycott the vote now that we have responded to all their demands and suggestions," Iraqi President Jalal Talabani said at a televised news conference after Tuesday's talks.
Sunni leaders fear the current proposals would lead the country to split into a Kurdish north and Shia south, depriving the Sunnis of access to the country's oil resources.
Earlier, one of the main Sunni parties, Iraqi Islamic party, said Tuesday's agreement meant they could call on their supporters to back the constitution.
Attacks have increased ahead of Saturday's referendum
But other Sunnis maintained their call for a boycott.
If voters in just three of Iraq's 18 provinces muster a two-thirds majority against the constitution, it will fail.
The Sunnis are dominant in four provinces and so therefore effectively hold a power of veto if they vote together.
However, correspondents say it will be difficult to attain such a vote and it is likely the constitution will be approved.