Iraq's top Shiite cleric has decided to withhold his endorsement of a Shiite coalition that swept last January's general election, rejecting repeated pleas by senior politicians for him to reconsider, associates on both sides said Wednesday. The move by the Iranian-born Grand Ayatollah Ali al-Sistani reflected the cleric's disappointment with the performance of Prime Minister Ibrahim al-Jaafari's Shiite-led government, according to three associates of the cleric who are in regular contact with him. Their comments represent the first known rift between the prominent ayatollah and the Shiite political parties he has supported since the ouster of Saddam Hussein in 2003.A senior official of al-Jaafari's Dawa party, Ali al-Adeeb, confirmed that al-Sistani had not "yet" agreed to endorse the Shiite alliance. Lack of an al-Sistani endorsement will reduce the chances that the Shiite coalition, formally known as the United Iraqi Alliance, can repeat its Jan. 30 success in the next election, set for Dec. 15. Al-Sistani's support was credited for enabling the alliance to win 140 of parliament's 275 seats, allowing it to form a government with the Kurds. Failure to repeat such success could significantly alter Iraq's political landscape, raising the possibility of a coalition government — perhaps without the big Shiite religious parties with ties to Iran.