Shiites constitute 62 per cent of the Iraqi population. Yet for five centuries, the Ottoman and British invaders who preceded Saddam Hussein, using the classic divide-and-rule tactics, installed successive Sunni minority governments. By destroying the Sunni-dominated Saddam regime, Bush gave the Iraqi Shiites an unprecedented opportunity to rule that they are now determined to exploit. More important, in geopolitical terms, he restored much of the Iranian influence in Baghdad that the Turks took away as a consequence of the 1639 Treaty of Qasr-i-Shirin after their conquest of Mesopotamia.

Did Bush recognize that destroying a Sunni-controlled dictatorship would lead to Shiite domination in Iraq, thus restoring Iranian influence there?
The President clearly did not have the Shiite connection on his mind. On January 10, 2003, just two months before the invasion, author Kanan Makiya and two other Iraqi exiles opposed to Saddam Hussein met with Bush to discuss scenarios for a post-invasion Iraq. They were astonished to find that Bush had never heard of the Sunni-Shiite divide in Islam.

The President's Pentagon advisers were better informed, but they, too, were not worried about empowering Iran. On the contrary, Douglas Feith, then-Undersecretary of Defence for Policy, told me that the Shiite clergy in Iraq, who support the separation of church and state, are “enormously threatening” to Iranian ayatollahs who believe they have a divine right to rule. The net result of the invasion, he said, could well be “the unravelling of the regime in Tehran, with Iranians inspired by the example of the Iraqi revolution”.

Given its focus on regime change in Teheran, the Bush Administration failed to recognize the strong ties the Islamic Republic had built with anti-Saddam Iraqi Shiite leaders. Iran has close ties with both the strongest militias in Iraq - the Mahdi Army, which controls the areas of Baghdad closest to U.S. headquarters in the Green Zone, and Abdel Aziz al Hakim's Badr Brigade, which sided with Tehran during the 1980-88 Iran-Iraq war.

What this means today is that the United States cannot get its combat forces out gracefully or stabilize Iraq thereafter without Iran's cooperation. Tehran will continue to send weaponry to its Shiite clients until Washington is ready for a deal that ends the U.S. occupation gradually and accepts Iran as a major player in post-war Baghdad along with the U.S. and eventually Saudi Arabia.

The Bush administration's threats to punish Iran militarily for its aid to the militias would be credible only if it is prepared for an all-out war. If U.S. forces bomb Iranian bases in retaliation, it could provoke such a war, and Tehran's allies in Iraq could make the U.S. presence increasingly untenable by firing high-powered rockets into the Green Zone.

During two recent visits to Tehran, I was told repeatedly by Iranian officials that Tehran has been restraining Sadr so far and is ready to cooperate in stabilizing Iraq.

“We find it absurd that you should accuse us of 'interfering' in Iraq,” said Mahmoud Vaezi, a former deputy foreign minister who now heads a think tank that advises the National Security Council. “You have come from 6,000 miles away with 160,000 soldiers. Iran is an immediate neighbour of Iraq with a 1,000-mile common border and intimate historical, religious and economic ties going back for centuries. The United States helped Saddam during a war that cost us more than 300,000 lives, so naturally we want to be sure that Iraq is in friendly hands."

By a “friendly” Iraq, Iran means one dominated by its Shiite co-religionists. Tehran has carefully avoided taking sides in the internal Shiite power struggle and wants Washington to do the same.

In the bargain envisaged by the Iranian officials I met, U.S. forces would end their current military offensive against Sadr and Iran would stop him from firing missiles into the Green Zone. The U.S. would withdraw all combat forces within, say, two years, and Iran would end all aid to the militias once U.S. forces are withdrawn. Iran would share intelligence on Al Qaeda. The U.S. would stop building up Sunni militias that now number some 91,000 fighters.

In Iranian eyes, the Sunni militias are part of a “divide and rule” U.S. strategy designed to offset Shiite power in Iraq and make it a U.S. protectorate with permanent U.S. bases. Teheran does not expect the U.S. to shut down all of its bases but wants security guarantees ruling out their use for attacks on Iran.

What would happen to the Sunnis if the U.S. withdraws and if Iraq tilts to Tehran? They would have to accept the rule of the Shiite majority, just as the Shiites have accepted Sunni domination. To help prevent their persecution, a U.S.-Iran bargain should be accompanied by broader regional arrangements in which Saudi Arabia joins in stabilizing Iraq. But such arrangements will work only if they are based on a clear recognition that Iran is entitled by virtue of geography, history, and religious ties, to have a bigger say in Iraq's destiny than its other immediate neighbours, not to mention the faraway United States.

Selig S. Harrison is director of the Asia Program at the Center for International Policy.