Senior Shi'ite and Kurdish leaders in Iraq say they are hopeful that an eleventh-hour offer to consider amending the country's draft constitution will convince Sunni Arabs to support the controversial charter in Saturday's referendum. At least one Sunni party said it would ask its followers to vote for the constitution.

The breakthrough came during last-minute talks Tuesday between Shi'ite and Kurdish leaders, who have been attempting for weeks to find ways to soften Sunni opposition against the draft constitution.

Shi'ites and Kurds, who largely wrote the charter and approved it without Sunni consent, say they are now willing to discuss amending the document next year, following the December elections for a permanent government.

Amending key provisions in the constitution has long been a demand of the Sunni Arabs, who say the charter as it is written is a blueprint for breaking up Iraq. Sunni leaders have been campaigning for a "no" vote in Saturday's referendum, opposing, among other things, a clause in the draft which calls for the creation of Shi'ite and Kurdish mini-states in the oil-rich north and south. That federalist arrangement raised Sunni fears that they would be left poor and politically weak in the middle of the country.

Late Tuesday, Iraq's main Sunni political organization, the Iraqi Islamic Party, says the offer to amend the constitution had been accepted and the group was preparing to call on Sunni voters to approve the draft on Saturday.

But without a firm agreement on how exactly the constitution would be amended, it is not yet clear if all Sunnis would agree to support a deal which could potentially leave them disappointed in next year's negotiations.

Iraq's Shi'ite and Kurdish-dominated National Assembly has called for an emergency session Wednesday night to ratify the agreement.