The rise of a secular, democratic Iraq could pose a threat to Iran's Shi'ite clerical establishment, which fears it would serve as a powerful model for moderate Iranians who seek change, clerics said.
Many senior clerics are particularly concerned about any shift in the center of gravity within Shi'ite Islam away from Iran's holy city of Qom, from which clerics wield immense political authority, toward Najaf in neighboring Iraq.
The emergence of Najaf coincides with the rise to political prominence of Iraqi clerics, such as Grand Ayatollah Ali al-Husseini al-Sistani, who question the legitimacy of absolute rule by the clergy.
"Now Najaf, as a more moderate center, will regain the place it held for most of the past 1,500 years," said Hadi Qabel, a reformist midranking cleric from Qom.
"It will rejuvenate the role of clerics throughout the Shi'ite world. ... Iraqi moderate clerics like Ayatollah Ali Sistani do not consider ruling the country as their legitimate right," he said.
Monday's formal transfer of sovereignty from a U.S.-led coalition to an Iraqi interim government represents a further opportunity for the rehabilitation of Iraq's Shi'ite community, which was brutally suppressed under Saddam Hussein.
Iran fears Washington may promote Iraq as a model for Shi'ites to emulate in pressing for change in the Islamic state, which Washington accuses of harboring terrorists and pursuing nuclear weapons.
Since a revolution 25 years ago toppled a shah supported by Washington, Iran's Shi'ite supremacy has driven a policy hostile to the United States even as the country has wrestled with the issue of internal reform.
Reformists, including Iranian President Mohammed Khatami, have repeatedly warned their rival hard-liners against creating an anti-democratic "path of extremism" that he says risks alienating people from Islam.
They argue that blocking reform that could eventually see Iran become a democratic Islamic state could paradoxically help to promote Najaf as an alternative center.
"Iran's experience in the last 25 years proved that clerical rule did not strengthen the religion. Rather, it resulted in diminishing the standing of clergy and religion in the society," Sheik Qabel said from Qom.
Fostering a supervisory role for clerics in Iraq and the creation of a more moderate center for Shi'ites in Najaf may challenge the authority and prestige of Qom's seminaries, analysts said.
"For this reason, Najaf will become more influential," said an analyst who asked not be named.
Despite the prevailing view, many Qom clerics support the idea of a separation between mosque and state that some Iraqi clerics have suggested, Sheik Qabel said.
"If security returns to Iraq, many clerics from Qom and other cities who share the same beliefs will move to Najaf," he said.
Saddam, a Sunni Muslim, killed tens of thousands of Shi'ites who form the majority in Iraq but were deemed a political threat.
By contrast, Shi'ite clerics rose to power after the 1979 Islamic revolution in Iran, which is also predominantly Shi'ite. Qom in central Iran became the center of political and religious authority.
"Saddam suppressed Shi'ite clerics brutally, but they have enough freedom now to reach the Shi'ite world," the analyst said.
Iranian Vice President Mohammad Ali Abtahi, also a moderate midranking cleric, believes Najaf's seminary will gain power as a nonpolitical Shi'ite learning center.
"Ancient Najaf seminary will become more powerful and will convey its supervisory views to the Iraqi government," Mr. Abtahi said.
But he rejected the idea that Najaf's seminary was a threat to Iran's theological centers.
"Even right now, there are different views in Qom seminaries, and I do not believe it will cause a huge exodus of Qom clerics to Najaf," he added.