The young Shiite mullah once claimed he would lead Iraq "back to true Islam," but he has been in Iran for at least the last six months. He had been expected to announce an end to the cease-fire observed by his Mahdi Army since 2007. Instead, he voiced a litany of woes that ended with an implicit pledge not to reactivate his death squads.

Muqtada blamed members of his entourage and unnamed mullahs and Shiite notables for having "undermined the struggle" for "worldly reasons" and for having succumbed to the temptation of wealth and power presented to them by the Iraqi government.

The 32-year-old ex-militia leader ended his letter by announcing that he is withdrawing from public life to pursue clerical studies "in accordance with the will and testament of my late father," Grand Ayatollah Muhammad Sadeq al-Sadr.

Muqtada now lives in Tehran but spends part of each week in the Iranian "holy" city of Qom, where he's taking a crash course in Shiite theology under the guidance of Ayatollah Nasser Makarem-Shirazi, a pro-government mullah with extensive business interests. Iranian sources say Tehran has decided to transform Muqtada into a genuine mullah who could be presented as a religious leader for Iraq in the next five to 10 years.

The real reason for Tehran's decision to withdraw Muqtada from active politics, however, may lie elsewhere.

In recent months, Tehran policymakers have begun to understand a crucial fact about Iraq: Any weakening of Prime Minister Nouri al-Maliki's government now could persuade the United States to throw its support behind an alternative, anti-Iranian coalition of Arab Sunnis, Kurds and secular Shiites openly hostile to Iran.

Thus, Tehran and Washington have a joint interest in keeping al-Maliki's coalition in power - at least until next year's Iraqi general election.

A worsening of Iraq's situation would increase the pressure on the next US president to start disengaging from what many Americans already see as a dicey adventure. And a US departure would produce a gap that only other outside powers would be able to fill.

The conventional wisdom in many places is that the key outside power likely to fill that gap is Iran. Iran does wield immense influence in Iraq, yet it's in no position to dictate Iraq's future political course. Even the Iraqi Shiite factions who look to Iran as the ultimate guarantor of their safety don't wish to see Iran as the dominant influence in Baghdad.

An early US withdrawal could lead to the disintegration of the Shiite-Kurdish coalition that is at least not hostile to Iran. As President Mahmoud Ahmadinejad's disastrous visit to Iraq this month showed, a good segment of Iraqi opinion regards the Islamic Republic as a troublemaker if not an outright enemy.

So we have a paradoxical situation in which the Islamic Republic actually fears that a precipitous US departure from Iraq could enable anti-Iran elements to come to power with the help of Arab Sunni states and Turkey.

Thus, the decision to leash Muqtada is part of a broader Iranian scheme to buy time. In the meantime, Tehran wants the Americans to keep on bleeding but not so profusely that the next president disengages from Iraq.

Tehran is also developing its ties with anti-US Sunni groups, especially by supplying them with sophisticated explosive devices. The idea is that, at some point, Tehran would be able to put together a coalition in Iraq transcending the Sunni-Shiite cleavage in the name of a common struggle against the American "Great Satan."

While Washington decision-makers are forced to think short-term, from one election to another, Tehran's powers take a longer-term view. In the case of Iraq, they are thinking for the next decade or so, just as they did in the case of Lebanon and, later, the Palestinian territories.

The Iraqi government and its coalition allies shouldn't stand idly by and watch the Islamic Republic impose its strategy on Iraq. Maliki should acknowledge the importance of the constituency that once backed Muqtada. (In the last general election, it won 11-plus percent of the votes.)

With Muqtada deciding to go to school, millions of poor Shiites, especially in Baghdad's slums, are left leaderless and vulnerable to the siren song of criminal gangs. Maliki could build a bridge to them by offering them jobs, better health care and, above all, security against racketeers and other criminals.

Numerous former Muqtada associates are prepared to work with the government locally and nationally. But many are shut out of power circles because of old rivalries with the largest Shiite political faction, led by Abdul-Aziz al-Hakim, a mid-ranking mullah with a history of family feuds with Muqtada al-Sadr.

Hakim's friends, including America, should encourage him to forget past grievances. A large chunk of Shiite support is floating around like a dangerous iceberg - but could be stabilized as part of the broader national coalition. Shiite unity remains the key to long-term stability and democratization in Iraq.

Muqtada shattered Shiite unity when, encouraged by Tehran, he rose in revolt against the elected government in Baghdad. With him out of the picture, no one knows how long the opportunity to rebuild that unity will last.

The re-inclusion of Muqtada's followers in the political process will make it easier for Maliki to hold long-overdue local and municipal elections sooner rather than later. These elections are necessary to allow the new leadership groups that have emerged at the grass-roots level all over Iraq to find their proper place within the decision-making process.