"Today is a historic day," he said. "I am confident that there will be a consensus on the constitution on the day of the vote."
The announcement caps days of last-minute negotiations between some Sunni Arab parties and Shi'a and Kurdish leaders to find compromises that will persuade Sunni Arabs to endorse the charter.
The talks included the best-known Sunni Arab party -- the Iraqi Islamic Party.
Baha Aldin al-Naqshabandi, a spokesman for the Iraqi Islamic Party, told RFE/RL from Baghdad today that any later constitutional review would focus on points that Sunni Arabs still insist on seeing in the constitution but have so far been denied: "The amendments about federalism, about the diversity of Iraq and its belonging to the Arabic nation, and some other amendments, but these are the main points."
Under the deal, the new National Assembly to be elected later this year would create a constitutional review committee. That panel would have four months to propose amendments that would address Sunni Arab and other concerns with the charter.
Al-Naqshabandi said his party wants later amendments to the constitution to restrict self-rule in the new federal Iraq to the Kurdish-administered north of the country.
"Regarding federalism, the Iraqi Islamic Party only admits the federalism of Kurdistan," al-Naqshabandi said. "But for the other regions of Iraq, the Iraqi Islamic Party cannot accept this federalism because it will divide Iraq into many countries."
Shi'a parties have insisted that Shi'a-majority areas of southern and central Iraq have the right to form a self-rule region if they choose to do so. That possibility is now enshrined in the draft constitution approved by the parliament last month but rejected by Sunni Arab leaders.
The Iraqi Islamic Party spokesman said U.S. pressure helped push Shi'a and Kurdish leaders to agree to a review of the constitution after the referendum. He also said he is optimistic the Sunni Arab demands will be met.
"It's more possible, I think, because of the assistance of the American embassy and the pressure of [U.S.] Ambassador [Zalmay] Khalilzad on the [Shi'a and Kurdish] coalition lists," al-Naqshabandi said.
The parliament today was also expected to adopt an amendment to the draft constitution requested by Sunni negotiators to moderate Iraq's so-called "de-Ba'athification"' process. That process is intended to root out former members of Saddam Hussein's Ba'ath Party from public office.
The last-minute negotiations over the draft constitution come as copies of the charter already have been distributed to the Iraqi public.
Families received copies of the charter through the state-controlled food-rationing system so that they may study the details before deciding whether to vote "Yes"' or "No"' to adopt it.
But some observers say the continuing last-minute negotiations over the draft constitution -- and now the possibility that there will be new amendments after the referendum -- make it difficult for ordinary Iraqis to know exactly what they are voting for.
"At the moment, the United Nations has printed 5 million copies in Arabic of the constitution and has begun to distribute these to all the regions of Iraq, there are also a number of copies in Kurdish that are being sent to the north," explained Joos Hiltermann of the International Crisis Group (ICG) in Amman. "That is the version that was considered final on September 13. But now there are negotiations under way in Baghdad to amend this constitution, it's not clear yet how profoundly. But one thing is certain, and that is that whatever changes are agreed upon by the negotiators are not going to be distributed to the people in this version."
Instead, he said, any changes will have to be announced through the media in the remaining hours before the referendum.
Many observers call the last minute changes to the constitution necessary to assure Sunni participation in Iraq's transition process and to avoid a split of the country along sectarian lines.
But Hiltermann said the result is a strange spectacle in which the rules often appear to being made up along the way.
"The participation of Sunni Arabs in particular, and the Iraqi Islamic Party is one of the parties based in the Sunni Arab community, is going to be critical for the long-term success of this constitution, so it is not surprising, though disappointing, and I must say a bit of a strange spectacle to hear and to see that the constitution will have to be changed through committee or whatever mechanism shortly after the referendum," Hiltermann said.
It is not immediately known whether any post-referendum changes would have to again be approved by a national referendum.
Meanwhile, it remains unclear how many Sunni Arabs will endorse the draft constitution on 15 October, as some leaders continue to call for the community to reject the document or to boycott the poll.