[JURIST] Grand Ayatollah Ali al-Sistani [official website], Iraq's most powerful Shiite cleric, said Thursday that he endorsed the draft Iraqi constitution [English translation; JURIST news archive] and called for officials in the Shiite Muslim hierarchy to promote a "yes" vote in the upcoming national referendum. Al-Sistani's endorsement comes as Sunni Arab clerics and tribal leaders called for rejection of the charter [AP report]. Sunni leaders are holding three days of meetings designed to firm up their opposition to the draft [JURIST document], which largely centers on the role of federalism. Meanwhile, Saudi Arabia's foreign minister warned that provisions in the proposed constitution that give more power to Iraqi regions show that Iraq is moving toward disintegration and cautioned that neighboring countries could be drawn into conflicts [USA Today report] between Shiites and Sunnis. Iraqis will vote on the draft constitution on October 15; under Iraq's Transitional Administrative Law [text], a majority must vote in favor of the charter, but if two-thirds of voters in any three of Iraq's provinces reject the draft, the constitution will be defeated. AP has more.