A day after Iraq's parliament approved the final version of the country's draft constitution, and two days before Iraqis were to vote on it in a nationwide referendum, members of the Sunni Arab minority were as divided as their leaders Thursday over what to do: vote yes, vote no, or not vote at all.

Since changes were still being made to the document as late as Tuesday night and no revised copies had been distributed, "I have no idea what the main benefits of the new constitution are," said Waad Shakir Mahmoud, 45, owner of a supermarket in Adhamiyah, Baghdad's largest Sunni Muslim neighborhood. "How am I going to vote on something I don't have any idea about?"

But others in his neighborhood -- where a banner on the local mosque declared "No to the constitution, no to the occupation, and no to deceiving the people" -- said they would vote in favor of the constitution. They said it offered the best hope for curbing rampant violence, ending foreign occupation and preserving Iraq's unity.

"This country is wounded, and we have to heal the wounds, despite what is being said about the constitution," said Aqil Naji, 30, the owner of a nut shop.

In the northern city of Mosul, a Sunni laborer, Ali Ubaidi, 37, said compromises announced Wednesday crafted to win Sunni support for the constitution made for "a good agreement" and had "changed people's attitude."

"I decided to vote yes in the referendum a long time ago, but that was a secret -- I couldn't tell people," he said. "But now, I will shout it in the street."

The last-minute changes to the draft constitution were made without a formal vote by Iraq's parliament on Wednesday, almost two months after the document was legally supposed to be finalized. Two Sunni political organizations, the Iraqi Islamic Party and the government-administered Sunni Endowment, have publicly endorsed the changes and urged followers to vote yes. Other influential Sunni groups were telling followers to vote no or skip voting altogether.

The referendum will fail if two-thirds of the voters in three of Iraq's 18 provinces vote against the constitution, a threshold that numerically would be almost impossible to reach if the Sunnis split their votes.

The first ballots were cast Thursday by thousands of Iraqi prisoners being held at detention centers around the country. Election officials said they did not know whether former president Saddam Hussein voted. His trial on war-crimes charges is scheduled to begin next week.

Until Wednesday, Sunni Arab leaders stood united against the constitution, arguing, among other things, that it would permit the creation of an autonomous Kurdish region in the north and possibly a Shiite Muslim ministate in the south, which would relegate Sunnis to the resource-poor, landlocked central and western regions. Such a situation could lead to continuing warfare and potentially the breakup of the country, they said.

The key compromise reached late Tuesday -- with the help of U.S. Ambassador Zalmay Khalilzad -- was to allow the next National Assembly, which is to be elected in December, to make amendments to the constitution, which would then be submitted to a national referendum.

But the most influential Sunni organization in Iraq, the Association of Muslim Scholars, said the Iraqi Islamic Party had been "deceived" by changes that were included solely to win passage of the constitution on Saturday.

A radical insurgent group, the Army of the Victorious Sect, termed the leaders of the Iraqi Islamic Party "apostates" for supporting the changes and threatened to kill them, Arab satellite television stations reported.

Rasheed Muhammed, 29, a taxi driver in Ramadi, an insurgent stronghold west of Baghdad, said although he hated Abu Musab Zarqawi, the head of al Qaeda in Iraq, "I agree with him that we should reject the constitution. If we say yes, it means we approve of the political process under occupation."

Correspondent Jonathan Finer in Najaf and special correspondent Dlovan Brwari in Mosul

contributed to this report.

Thousands of prisoners, such as these in jail in Samawah in southern Iraq, cast the first ballots in the national referendum on Iraq's constitution.