Iraq's powerful Shiite cleric Moqtada al-Sadr, whose opinion holds sway over tens of thousands of supporters, called on his followers on Monday to join Friday protests in Baghdad, a move that could risk escalating tensions over government reforms. The capital and many southern cities have witnessed demonstrations in recent weeks calling for the provision of basic services, the trial of corrupt politicians, and the shakeup of a system riddled with graft and incompetence. Sadr's statement is the first direct appeal by a major party leader to participate in the protests.