The signing of the constitution has been delayed twice - first by bomb attacks on Shia on 2 March that killed at least 181 people, and then by last-minute doubts among Shia members that forced a high-profile ceremony on Friday to be abandoned.
Representatives of the five groups that backed out on Friday spent the weekend in the Iraqi city of Najaf talking with top clerics including Ayat Allah Ali al-Sistani, who wields immense influence over Iraq's Shia community.
They announced on Sunday that al-Sistani still had deep reservations about the document, but had given them the go-ahead to sign it in the interests of advancing political transition.
Under a US timetable, an Iraqi government is to take over sovereignty on 30 June, and elections for a transitional assembly are to be held by the end of January next year.
Council members arrived on Monday morning for brief talks and were expected to sign the document within hours.
"We will sign it today without any changes," Mahmud Uthman, an independent Kurdish member of the Council, said.
The main point of dispute has been a clause in the constitution that may allow Iraq's Kurdish minority to veto a planned permanent constitution if it does not enshrine their right to autonomy in three northern provinces.
"We will sign it today without any changes"
Independent Kurdish member of IGC
The Kurds, who have ruled three provinces of northern Iraq since wresting them from Saddam Hussein's control after the 1991 Gulf war, had said if the clause was not included they would not sign, and the issue risked opening a new rift among Iraq's ethnic and religious groups.
US troops and Iraqi security forces in Baghdad are on high alert against any attempt by guerrillas to disrupt the signing of the constitution.
On Sunday evening police said 10 rockets were fired at the headquarters of the US-led administration in Baghdad, close to where the document is to be signed. There were no serious injuries.
Al-Sistani still has ''reservations''
but gave go-ahead to sign
Iraq's US governor Paul Bremer said in interviews on US television he was confident the signing would go ahead on Monday. "We've noted the statement by the current president of the Governing Council that they do intend to sign it," he said.
Muhammad Husayn Al-Hakim, who is the son of a top Najaf cleric and sat in on the discussions at the weekend, said clerics were unhappy with the document, but understood its importance.
"The religious authorities have made their position clear to the politicians, but don't want to interfere directly," Husayn Al-Hakim said. "They have deep reservations, but also know this interim constitution is a step in the right direction."
"The religious authorities have made their position clear to the politicians, but don't want to interfere directly. They have deep reservations, but also know this interim constitution is a step in the right direction"
Muhammad Husayn Al-Hakim,
Member of Shia community who sat in on talks
Others present said al-Sistani would have liked to push for changes, but felt the furthest he could go was to make his objections clear and leave it up to the politicians to do what they felt necessary.
Al-Sistani, a 73-year-old Iranian-born religious scholar, has increasingly exerted his influence on politics in recent months.
He has expressed objections to the US timetable for handing back power, forcing the Americans to bring forward planned elections. Al-Sistani was also strongly against giving the Kurds veto power over a permanent constitution.