One theory on the Basra disaster

I thought this was very interesting (although it's not really sourced.)

What Petraeus did not reveal is that al-Maliki was deliberately upsetting a Petraeus plan to put US and British forces into Basra for a months-long operation to eliminate the Mahdi Army from the city.

According to this, Cheney's visit did spawn this action, but not as intended. After that meeting, Maliki had decided to short circuit the US plan.

When the Basra operation became an obvious disaster, however, Washington officials began to question al-Maliki's motives..... one official told the Washington Post's Peter Baker they were comparing conspiracy theories about why al-Maliki had acted so precipitously.

Although that comment was not explained, it clearly implied that al-Maliki was deliberately undermining the US objective of eliminating the Mahdi Army by using US and British troops.

Bush administration suspicions of al-Maliki's intentions could not have been eased by the fact that a delegation of pro-government parties traveled to Iran to ask the commander of the Iranian Revolutionary Guard Corps (IRGC) to negotiate a ceasefire with the Mahdi Army. That ploy move, which did result in a tenuous ceasefire, raised the possibility that al-Maliki intended from the beginning that the outcome of the Basra operation would be a new agreement that would prevent the deployment of US and British troops to fight the Mahdi Army during the summer.

So, according to this, the goal was to keep the US and British from taking on a major anti-Mahdi operation. Why? To keep the US/British from reestablishing in the region? Was it fear that such an operation would tip the Shia away from Maliki and more towards Sadr?