Reclusive cleric greatest challenge to US-led coalition in Iraq

He may represent the greatest challenge to the US-led coalition's plans for restoring sovereignty to Iraq, but powerful cleric Ali al-Sistani hides behind an arcane and near-impenetrable curtain of Shi'ite Muslim ritual and austerity.

Sistani, revered by Iraq's Shiite majority, dwells in a humble office at the end of a dusty lane in the holy city of Najaf, 180 kilometres (110 miles) south of Baghdad.

But few doubt the power of the cleric who has mustered tens of thousands behind a rallying call for direct elections in place of the coalition's scheme to install a new leadership through regional caucuses by June 30.