As American forces complete their withdrawal from Iraq in coming days, concern has grown in Washington that neighboring Iran is determined to fill any "vacuum" with its own influence.

Iraqi officials have long dismissed that scenario as overblown. But an attempt by Tehran to install a top-ranking cleric in one of Iraq's holiest cities – thereby exercising far greater influence over Iraq's religious and political life – has prompted warnings of an "Iran project" to boldly increase leverage with its neighbor.

Iran has enjoyed sway in Iraq since the 2003 US invasion through large investments and charity work to help the country's majority Shiites, as well as by supporting Shiite militias to take on US forces on Iraqi soil.

But so far, Iran's ability to affect Iraq's powerful religious establishment – headed by the revered Grand Ayatollah Ali al-Sistani, in the holy city of Najaf – has been limited.

Now, in conjunction with Iraqi Prime Minister Nouri al-Maliki's Dawa Party, Tehran is trying to move one of Iran's heaviest-hitting clerics to Najaf.

Analysts say the bid to install Ayatollah Mahmoud Hashemi Shahroudi – a former Iranian judiciary chief who is very close to Iran's absolute ruler Ayatollah Ali Khamenei – aims to undermine Mr. Sistani, blunt his criticism of Mr. Maliki's government, and draw Iraq closer to Iran.

Mr. Shahroudi is just one man, but as a marja – the highest rank of cleric in Shiite Islam, a "source of emulation" for followers – he's among the elite few who might challenge Sistani for influence in Iraq and jeopardize American hopes to limit Iraq's ties to Iran.

It may not succeed. But the effort is a window into how Shiite Iran may try to exercise soft power in Iraq in years to come.

"I think that's just wishful thinking by Shahroudi, the Dawa Party, and the Islamic Republic [of Iran]," says Mehdi Khalaji, an Iran specialist at the Washington Institute for Near East Policy. "If such a thing happened, it would mean that he would be Khamenei's representative in Iraq.... That's the plan."

Both men are maraji. But they could not be more different. Sistani adheres to a "quietist" tradition that dabbles little in politics – although he frequently condemns the corruption and misrule of Maliki's government – and has far more followers.

In contrast, Shahroudi has few followers and would bring from Iran a firm belief in activist and supreme clerical rule known as velayat-e-faqih, as well as a brutal record against regime opponents that some say taints him.

"I believe they won't succeed, exactly because [Shahroudi] was labeled as the Islamic Republic's puppet for a long time," says Mr. Khalaji, who trained at Iran's Qom seminary for 14 years. "But they have lots of money, lots of influence, media, and propaganda, so they can pretend at least that he is a marja and he has lots of followers – but I don't think that description corresponds to reality."

'Clear evidence' of Iran intervening?

In public, the neighboring countries, who fought an eight-year war in the 1980s at a cost of nearly 400,000 dead, pledge friendship and respect.

"Iran and Iraq have brotherly relations and no factor can divide the two nations," Iran's president, Mahmoud Ahmadinejad, said last month. He said Iran and Iraq could help establish a "just order" in the world.

Maliki’s Dawa party has recently tried to distance itself from the choice of Shahroudi as its spiritual guide, saying that members are free to make their own religious choices.

Maliki himself, speaking on the eve of his current trip to Washington, said reasons for Iran to meddle in Iraq were dwindling: "If [Iran's] excuse was that the presence of U.S. troops on Iraqi soil posed a threat to [Iranian] national security, then this danger is over now," he told the Wall Street Journal.

For Iran, however, the "brotherly relations" described by Ahmadinejad might include the elevation of Shahroudi, who was born in Iraq and who on paper appears to have the perfect pedigree. But he also carries lots of Iranian political baggage, and the concept of absolute clerical rule that he subscribes to is not widely accepted in Iraq.

"Ayatollah Khamenei has taken a number of decisions as an urgent preemptive plan to counter the prospective challenges to Iranian influence in Iraq" after the US withdrawal, reported the Pan-Arab newspaper Asharq al-Awsat late last month, quoting an "Iranian dissident."

Those steps include intensifying support for Maliki, helping to unify divided Shiite leaders and parties, and “most importantly appointing a senior Iranian Shiite cleric as the velayat-e-faqih for Iraq” that would create "an alternative Shiite religious authority" in Iraq.

The source – unnamed, and in a newspaper funded by one of Iran's top regional rivals, Saudi Arabia – further asserted that the Shahroudi decision "represents clear evidence that Khamenei is determinedly planning to intervene in a broad scale in Iraq."

Iraqi lawmakers say they are not so vulnerable to such Iranian influence. "Shahroudi is more acceptable to Iran, and I think not so acceptable to Iraqis," says Shiite parliamentarian Ali Shubbar, who spent 21 years in exile in Iran.

"Sistani as marja is very different, fundamentally, than Shahroudi," notes Mr. Shubbar. "The maraji in Najaf will not go far ... from Sistani's [quietist] school of thought ... when they choose a successor." While Sistani was born in Iran, he moved to Iraq before the 1979 revolution and was never part of Iran's regime.

Opposition to Shahroudi erupted on the eve of his office's opening in Najaf in October. Sistani refused to see Shahroudi and was reported to not support his candidacy for a clerical leadership position in Iraq.

Shahroudi was meant to come to Iraq himself, but the snub derailed the visit. Sistani's office "believes that the ascendance of Shahroudi is an Iranian [government] project" to weaken religious authority in Najaf, an "informed source" told the Shatt al-Arab news outlet.

A cleric close to Iran's supreme leader

Shahroudi was trained decades ago by revered Iraqi Grand Ayatollah Mohammed Baqir al-Sadr, who gave rare written confirmation of Shahroudi's clerical credentials. He then went to Tehran to serve the father of Iran's 1979 Islamic revolution, Ayatollah Ruhollah Khomeini, who appointed him coordinator of all Shiite powers outside Iran – especially those in Iraq.

Respect for Grand Ayatollah Sadr, who was tortured and executed in 1980 by Saddam Hussein's regime, still resonates among Iraqi Shiites and helped boost the political fortunes of his son-in-law, the anti-American cleric Moqtada al-Sadr.

The younger Sadr staged two uprisings against American forces in Iraq, has a powerful faction of loyalists in parliament, and reportedly studies under Shahroudi in Iran.

Despite those links, some Shiite politicians try to play down the impact of any high-level changes.

"Our religious maraji are a very strong establishment," says Hassan al-Jubori, an Iraqi parliamentarian loyal to Sadr. "It is not conceivable that the coming of any marja from outside would have 1 percent influence on the Shiites of Iraq.

"It's true some politicians will take the opportunity to show how bad Iranian influence will be, but the fact is Iran has been a neighbor for hundreds of years," says Mr. Jubori. "We should look for ways of good exchange."

Of concern to many Iraqis is Shahroudi's hard-line history. As Iran’s judiciary chief he was instrumental in cracking down on student protests in 1999, closing more than 200 newspapers, and prosecuting reformist lawmakers.

Today Shahroudi sits on Iran’s Guardian Council, and – in a sign of how close he is to Khamenei – he was appointed earlier this year to head a five-member arbitration body meant to resolve severe political disputes between Ahmadinejad and Parliament.

"He has a very black record, and it's very obvious; there is no doubt that his hands are in blood," says analyst and former seminarian Khalaji, noting that senior clerics are meant to be objective, which a judge cannot be.

"This is something that destroys one's credential in the seminary; being a judge always puts your religious credentials at risk. That's why very prominent clerics are extremely reluctant to accept the position of a judge, let alone being the head of judiciary," he says.

Seen by some as brutal, not pious

Of course, in the Islamic Republic, the judiciary and a number of key ministries are controlled by clerics. But Shahroudi does not fit the mold of an ascetic, humble spiritual guide. "He's very wealthy, he's doing business," adds Khalaji. "[Shahroudi] lacks this pious image that is very necessary to be a marja and have a real wide range of followers."

But that did not keep Dawa from "inviting" him to Najaf to vie for influence against Sistani. The Iranian government "considers this project a vastly beneficial one," an unnamed Dawa source told Shatt al-Arab.The choice was "an attempt to get rid of the pressures" of Sistani's criticism, the source acknowledged.

He added that Shahroudi was instrumental in overcoming months of stalemate to help form the Iraqi government.

Shahroudi made "enormous efforts" to garner Iranian support for Maliki to remain as prime minister after a controversial vote, while pressuring Sadr to do the same in a "secret deal brokered by Shahroudi."

One Shiite critic claimed that Maliki, after taking control of the government, now wants to use Shahroudi as a "very powerful and influential weapon" to control its maraji.

But the problem of ties to Iran also remains, says Khalaji: "People in seminary do not have a good image of Shahroudi, because they believe he ... works for Khamenei."

Sahar Issa contributed reporting from Baghdad.