Gloom abounds in the administration's discussion of the dangers of Iranian ascendancy in the Middle East generally and its negative role in Iraq specifically. But Iran faces a choice regarding the nature of its ascendancy and the United States can influence that choice by shaping the Iranian role in Iraq.

The Iranian ambassador to Iraq, in an interview on January 28 with the New York Times correspondent in Baghdad, indicated that Iran intends to expand its role in Iraq, including "work on security." Instead of trying to block Iran's role in Iraq, and forcing Iran to make the wrong choice regarding the overall direction of its Middle Eastern ascendancy, Washington should think about how to structure Iran's security role in Iraq. In order to orient Tehran in the right direction, Washington should integrate the Iranian security role in Iraq into the American security apparatus there.

One option, fraught with peril and obstacles, is for Iran to carve out a wider Shi‘a role in the Arab world by attempting to subvert Sunni influence, take the lead in the "war" against Israel and roll back U.S. influence in the region. But Sunni tradition is too entrenched in Arab culture to ever be displaced by the non-Arab version of Islam that Shi‘a Iran represents. And this path to Iranian ascendancy will heighten both U.S. explicit backing for Israel and tacit Sunni backing. In addition, if Iran tries to engineer in Iraq a Shi‘a displacement of the Sunnis, it will find Sunni insurgent terrorism increasingly directed at Iranian targets. Iran cannot rationally want the Sunni insurgency-with its growing indigenous Al-Qaeda backing-to make a safe haven for terrorism in Iraq. Tehran certainly does not want to inherit the Sunni insurgency in Iraq from the United States.

On the other hand, by acting to bring about a politically constitutive Sunni-Shi‘a reconciliation in Iraq, Iran would make Arab Sunni leaderships more supportive of its ascendancy, insofar as this would contribute to stabilizing restive Sunni- Shi‘a relations in their own countries. This second path of Iranian ascendancy can arise only from the United States taking a collaborative approach to Iran's involvement in Iraq. It is up to the United States to facilitate Iran in becoming an architect of Sunni-Shi‘a reconciliation, rather than an instigator of a Shi‘a victory over the Sunnis.

On its own, Iran will support the Iraqi Shi‘a against the Sunnis. But if the United States concentrates on controlling Sunni violence and pointing the Sunnis toward political reconciliation with the Shi‘a, Iran would be encouraged to reciprocate by taking control of the Shi‘a and pointing them in the direction of reconciliation.

These considerations raise the possibility of the creation of a dual Iranian-U.S. structure of military control in Iraq. With the British preparing to evacuate their troops from the four southern Iraqi provinces where they are currently stationed, the United States should open talks with Tehran about the Iranian military taking over security responsibilities in the Iraqi Shi‘a southeast, as well as the Sadr City quadrant of Baghdad. In the southwest, where the population is a mix of Shi‘a-Arab and Sunni-Arab, U.S. and Iranian security operations would overlap and have to be coordinated, as would be the case in Baghdad itself. Northern Iraq is mostly Sunni-Kurds, with a southern portion of the population that is Sunni-Arab and Sunni-Kurd. This whole area would be a U.S. responsibility.

A structure of this sort would create powerful incentives for Iraqi Shi‘a and Sunnis to forge a political agreement. The absence of trust has been the major impediment. But with the dual American-Iranian controls on each of the two sects serving as shields for each against other, the conditions for trust would improve considerably.

The United States need not feel that it is leaving Israel in the lurch by collaborating with Iran. On the contrary, an Iran that is involved in a collaborative relationship with the United States in Iraq will be more measured in its approach to Israel. It is unlikely that Iran would crank up Hezbollah attacks on Israeli targets while it is cranking down Shi‘a attacks on the Sunnis in Iraq. Further, collaboration between Iran and the United States in Iraq would represent a second, Muslim pivot point for U.S. policy in the Middle East. Israel would no longer represent the sole pivot, which has been the case since the beginning of the Cold War. Arab nations would thereby become less resentful of the U.S.-Israeli relationship and feel less like second-class citizens in their own neighborhood. As they begin to perceive Israel's presence as less unacceptable, one can imagine some of the Arab states actually allying themselves with Israel in order to "balance" the U.S.-Iranian collaboration in Iraq.

Thus, the moral landscape of the Middle East would be transformed as a result of U.S.-Iranian collaboration in Iraq. In trying to block Iran by stoking the smoldering flames of ethnic and religious antagonism between the Arab states and Iran, the United States would forfeit a major opportunity to make its intervention in Iraq pave the way to a new and better era for the whole Middle East.

Thomas Millington is an emeritus professor of political science at Hobart and William Smith Colleges.