BAGHDAD, Iraq - With his powerful anti-American movement losing its footing amid U.S.-led round-ups and military operations, the Shiite Muslim cleric Muqtada al-Sadr is trying to recast himself in his one-time image as a national resistance figure for all Iraqis - Shiite and Sunni alike. In central Baghdad, a large billboard featuring al-Sadr's defiant visage proclaims: "I'm not Shiite/I'm not Sunni/But I am Iraqi." On Monday, the fourth anniversary of the U.S. conquest of Baghdad, al-Sadr ordered his followers to unite in the holy city of Najaf in a "mammoth demonstration" against the U.S. military presence and to "raise the...