Iraq ? A top Shiite cleric Saturday refused to support a U.S.-backed plan to form a political coalition of Iraq’s Shiites, Sunni Arabs and Kurds – an attempt to defuse the sectarian violence that has gripped the country.

Lawmakers who presented the plan to Grand Ayatollah Ali al-Sistani in the holy city of Najaf said they were told the unity of Shiites had to come first. Shiites have the largest bloc in the parliament.

By shunning the coalition plan, al-Sistani sought to unite the Shiite’s fractured 130-member United Iraqi Alliance. His decision significantly weakens American hopes for a national unity government and strengthens the hand of the radical Shiite cleric Muqtada al-Sadr.

The proposed coalition – which would not have included al-Sadr’s supporters – could have isolated the militant cleric, commander of a militia army blamed for many sectarian attacks.