The tentative deal was reportedly reached late last night during closed-door negotiations. U.S. diplomats were also reportedly involved in the talks over the past days.
According to reports, Shi'ite, Kurdish, and Sunni Arab negotiators agreed that, if the constitution is approved by voters on 15 October, the Iraqi parliament that is due to be chosen in December elections would be able to set up a commission to consider amendments to the document.
It was not immediately clear if the current parliament will need formally to approve the deal.
Other Sunni Arab groups continue to oppose the charter, saying they fear it could isolate Sunnis and lead to Iraq breaking up into competing regions.
Iraq: Kurds Sponsor Talks With Sunni Arabs On Draft Constitution
Iraq: Sunnis Weigh In On Draft Constitution
For RFE/RL's full coverage of the 15 October constitutional referendum in Iraq, see "Iraq Votes: Constitution Referendum"