He receives a select few, and hasn't left his home since April. His public pronouncements on politics are rare. He has refused to meet with American officials, including chief Iraq administrator L. Paul Bremer (search).

But Grand Ayatollah Ali al-Husseini al-Sistani (search) — a frail, 70-something Shiite Muslim (search) cleric with a heart condition — has emerged in post-Saddam Hussein Iraq as the land's most influential figure, something U.S. planners may not have counted on.

Iraq's American occupiers took their first measure of al-Sistani's influence when he issued a fatwa, or religious edict, in June that only an elected assembly should draft a new constitution. At the time, the Americans appeared hardly to notice the decree.

But when the U.S.-appointed Governing Council wouldn't accept their plan for an indirectly elected constitutional assembly, the Americans were forced to try again. The new plan, agreed on Nov. 15, calls for direct elections of delegates who would draw up a constitution.

Al-Sistani struck again this week. His target: a provision in the new plan to have a legislature, to be elected in regional caucuses, select a transitional government that would hold power until democratic elections by the end of 2005.

According to two members of the Governing Council who met with al-Sistani this week, the cleric prefers that the legislature be elected in a general, nationwide vote, not through caucuses.

Jalal Talabani (search), a Kurdish leader and the current president of the Governing Council, met with al-Sistani in the holy city of Najaf on Thursday. He later told journalists that he agreed with the cleric's views, which he described as "logical and reasonable."

That from the very man who — with Bremer — signed the agreement that al-Sistani was criticizing. Talabani, who made his way to al-Sistani's modest house on a narrow Najaf alley through scores of curious onlookers, appeared to have fallen under the spell of the elderly cleric.

"The agreement remains, but we may add an attachment that has additional clauses," said Talabani, a Sunni Muslim. "The agreement can evolve. ... I will take his views to the council and we, God willing, hope to ratify them."

Shiite Governing Council member Abdel-Aziz al-Hakim, who met al-Sistani Tuesday, said the cleric had expressed "deep concern over real loopholes" in the power-transfer plan and demanded instead direct elections for a transitional legislature.

Among the main objections (of al-Sistani) is the lack of a role by the Iraqi people in the process of transferring powers to the Iraqis."

At a news conference late Thursday, al-Hakim said negotiations have begun between the coalition and a Governing Council committee to discuss the issue of the legislature.

"The committee entered constructive talks with the occupation authorities and progress has been made ... we are filled with optimism that positive results will be reached," he said without elaborating.

Al-Sistani's objections are certain to complicate an already difficult task for a U.S.-led coalition eager to hand over sovereignty to Iraqis as soon as possible, as casualties mount from rebel attacks that are becoming more brazen and lethal.

The impact of al-Sistani's June fatwa and his latest position underscores the realities of the new Iraq, where the long-oppressed Shiite majority has emerged as the single, most-dominant social and political force. Just as important, it highlights the key political role played in today's Iraq by Shiite clerics.

During Saddam's 23-year rule, clerics — Shiite and Sunni alike — steered clear of politics for fear of brutal reprisals. Those who dared to speak out, like prominent Shiite leaders Mohammed Baqir al-Sadr and Mohammed Sadiq al-Sadr, paid with their lives. The first al-Sadr was executed in 1980; his cousin was killed by suspected Saddam agents in 1999. Other clerics fled the country to escape a similar fate.

The Iranian-born al-Sistani belongs to what is commonly known as the "quietest" tradition, placing his spiritual calling ahead of politics. But, according to some experts, he may have cast off some of his inhibitions to speak out about politics — hoping to influence the shaping of an Iraq emerging from decades of dictatorial rule and centuries of Shiite oppression at the hands of the country's Sunni Arab minority.

Al-Sistani is a moderate who doesn't believe, as do the ruling clergy in neighboring Shiite Iran, that the most learned of clerics should rule. He does insist that broad Islamic principles must be observed in a predominantly Muslim nation like Iraq.

But his refusal to play a more active role in politics has allowed younger, radical and less-educated Shiite clerics to win over poor Shiites in major cities like Baghdad and Basra, taking advantage of economic hardships and resentment of the U.S. occupation.

One of those is Muqtada al-Sadr, whose lineage and savvy street politics have hoisted him to leadership status in the seven months since Saddam was ousted.

Al-Sadr, son of the elder al-Sadr killed in 1999, has in the past derided al-Sistani for what he termed aloofness and for his non-Iraqi background. Al-Sistani's supporters maintain that while their leader was born in Iran, he is the descendant of a prominent Iraqi family.

"Al-Sistani is our safety valve, and a compass that directs our march," said Mouwafak al-Rabii, a Shiite Governing Council member and a longtime human rights campaigner.

"The remarks attributed to him are very important and vital," he told The Associated Press on Thursday. "They serve the interests of the Iraqi people, and I agree with them."