The Grand Ayatollah Sistani may call the tune, but the US will still have the power

The election in Iraq next Sunday is the result of pressure from Grand Ayatollah Ali al-Sistani, the 71-year-old cleric, who exercises such immense influence over the Shia community who make about 60 per cent of the Iraqi population.

US officials never mention today that in the months after the overthrow of Saddam Hussein they were opposed to an election, citing difficulties in identifying voters without a census and lack of security.

The real reason the US was so nervous of an election was that it feared that Shia parties, particularly those very religious and close to Iran, would win a majority. It hoped instead to rule Iraq through direct imperial control supplemented by returning Iraqi exiles acceptable to Washington.

It did not work. Gradually, the arrogant neoconservatives holed up in the Green Zone in the centre of Baghdad came to realise that the cleric, who seldom left his house down a narrow alley in Najaf, held them in the palm of his hand. Paul Bremmer, the American viceroy in Iraq, could travel all over the country but he never succeeded in meeting the Ayatollah Sistani.

In June, 2003, the cleric issued a fatwa, or religious ruling, saying those who framed Iraq's new constitution must be elected rather than selected by the US and members of the now defunct Iraqi Governing Council. In November, 2003, he issued a statement saying that elections, not elaborate, regional caucuses suggested by the US, should chose a transitional government.

As rebellion spread across the Sunni Muslim heartlands in northern and central Iraq the US came to realise it had to reach an agreement with the Grand Ayatollah. Under great military pressure from Sunni Arabs, 20 per cent of the population, Washington could not afford to fight the Shias as well. It agreed to an election.

Ayatollah Sistani's influence has increased since the invasion. Born near the holy city of Mashad in Iran, he moved to Najaf in 1952. He studied with the most important Shia cleric of his time, Grand Ayatollah Abul Qassim al-Khoei. In contrast to the Iranian clergy, he opposed a direct political role for Islamic clerics, favouring an Islamic state but not a theocracy. When Khoei died in 1992, Sistani was chosen to head the Hawza, the network of Islamic schools in Najaf, making him the most influential Shia cleric.

There was one mistake the Shia clergy were determined never to make again. After Britain had captured what became Iraq from the Turks in 1917, the Shias vigorously opposed the occupation. They rebelled in 1920 so the British co-opted the Sunni Arabs to rule Iraq as they had under the Ottomans. Not all the Shia leaders agreed. It is not a homogenous community.

Many Shias are secular. Exiled opposition leaders such as Ahmed Chalabi and Iyad Allawi, who returned after the fall of Saddam, came from rich Shia merchant families who had prospered under the monarchy. The community had been the base of the powerful Iraqi Communist Party in the 1950s. The Shias were generally glad to see the end of Saddam's regime. He had crushed in blood their uprising in 1991. But, unlike the Kurds, they did not welcome permanent US occupation.

The danger posed to the US if the Shias joined a rebellion against the occupation was demonstrated in April, 2004, when Muqtada al-Sadr, son of the religious leader Moham-med Baqr al-Sadr, murdered by Saddam in 1999, seized several cities and part of east Baghdad. His movement blended Shia religion and Iraqi nationalism. He commanded a powerful if ill-disciplined militia, the Mehdi Army.

The Grand Ayatollah's powerful influence was underlined last year. For the first time in six years, he left his house in Najaf to have medical treatment in London. While he was there, the Mehdi Army fought fierce battles against the US Marines for control of Najaf. Much of the city was destroyed. But on his return the Grand Ayatollah was able to produce a peace agreement which saved the Shrine of Imam Ali from destruction.

Under his auspices, a largely Shia slate, or coalition, was put together called the United Iraqi List. It includes all the main parties which are predominantly Shia. Mr Allawi has been gaining support but the so-called Shia list is still expected to top the poll on Sunday.

Victory in a fair election will show the Shias have the right to power but it will not necessarily give them real authority. The 275-member National Assembly requires agreements between the three main communities, Shia, Kurd and Sunni, to reach a decision. The US remains the most powerful force in the country. The Sunni insurgents control swaths of territory. The Shia have some way to go before they rule Iraq.