Into Najaf?

I don't think this is going to end well:
US marines said on Wednesday they were preparing a final assault on Iraqi Shi’ite militia in the holy city of Najaf, after a radical cleric urged his men to keep fighting even if he was killed. The warning came as sporadic clashes between U.S. troops and militia loyal to Moqtada al-Sadr echoed from the heart of Najaf, where hundreds have been killed or wounded in the past week around some of Iraq’s holiest Shi’ite Muslim sites. “Iraqi and U.S. forces are making final preparations as we get ready to finish this fight that the Moqtada militia started,” Colonel Anthony Haslam, commanding officer of the 11th Marine Expeditionary Unit in Najaf, said in a statement. Haslam gave few details, but his threats and Sadr’s defiance have raised the stakes in a battle that is the toughest test yet for the 6-week-old government of Prime Minister Iyad Allawi. In a sign of the growing anger against Allawi and the military action in Najaf, thousands of demonstrators in the southern city of Nassiriya called for him to step down and set fire to the local office of his political party. Most of Sadr’s men and the young cleric himself are holed up around Najaf’s ancient Shi’ite cemetery or the adjoining Imam Ali Shrine. Storming such holy symbols could touch off a firestorm among Iraq’s majority Shi’ite community.
The Iraqi population is 60% Shiite. I can't imagine how storming Shiite holy shrines will end well. I've seen reports in recent days that illustrate how the number of insurgents against the US has risen as the number of troops in Iraq have fallen. This is not a good situation for the US, and it is useful to point to this post by Kevin Drum, which re-examines the debate about the required troop levels to hold the peace after the war. I have to wonder whether or not this renewed interest in going after Sadr has anything to do with taking out potential political threats to the Allawi government. You can see the recent problems of Ahmed Chalabi in this light, as well. I don't have a good feeling about sieging Najaf and killing Sadr. I don't think it should be the US to lead this force, and I certainly don't think we have the troop levels to combat the likely increase in the insurgency, which will result from a Sadr martyrdom or the destruction of these Shiite holy shrines. Update: Pre-mature blogging:
After spending today preparing for a major attack against insurgents loyal to the rebel Shiite cleric Moktada al-Sar, American forces called off the attack as it was about to begin. Officers here described the reversal as a postponement and said the attack could still be carried out at any time. The abrupt reversal came after a day of hawkish announcements by American officers here. American forces have been close to capturing or killing Mr. Sadr before, but have repeatedly backed off. This time American commanders had vowed to crush his guerrillas, known as the Mahdi Army. [...] But a known concern of the American military is that fighting in Najaf's old city, where many of Mr. Sadr's guerrillas are hiding, could damage the shrine of Imam Ali, one of the holiest sites in Shia Islam. Damage to the mosque by either side could provoke immense anger among Iraq's 15 million Shiites, and marines and soldiers have been told that the consequences could be catastrophic. Any attack must still be approved by Ayad Allawi, Iraq's prime minister. Officers said they could not disclose whether Mr. Allawi had delayed the attack.