Pespective: The new plan: fight the Mahdi army toe to toe, hope Iraqi army holds

The Americans could be about to embark on the most dangerous phase of the conflict since the invasion of Iraq in 2003, pitting themselves for the first time against the Baghdad stronghold of the Shia cleric and militia leader Moqtada al-Sadr.

There was much media scepticism following George Bush's speech on Wednesday night over whether US forces would actually enter in strength into Sadr City, the huge slum area on the capital's east bank, home to two million Shia.

But the new defence secretary, Robert Gates, made a clear-cut pledge at a press conference in Washington yesterday morning. "All parts of Baghdad are going to be involved in this campaign, including Sadr City," he said.

Since 2003, US troops have taken on Sunni Muslim insurgents and left the Mahdi Army largely alone, apart from a short-lived battle in Najaf in 2005. But the new strategy outlined by Mr Bush identified sectarian violence as being at the centre of the conflict and that means tackling Shia gunmen as well as Sunnis.

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