By Serena Chaudhry and Raheem Salman
NAJAF, Iraq (Reuters) - Cleric Moqtada al-Sadr, head of a powerful Shi'ite movement in Iraq, on Sunday called for more political reforms, saying he would back a no-confidence vote against the prime minister if they were not made.
Sadr, a Shi'ite cleric who led uprisings against the U.S. presence before American forces withdrew last December, is now an influential player in government after his bloc's support of Iraqi Prime Minister Nuri al-Maliki helped secure his position.
"Our main demand and the last demand is reforms," Sadr told journalists during a rare news conference at his family home in the Shi'ite holy city of Najaf, southern Iraq.
"I said and I am still saying that there is a promise from me to the other blocs if the votes (for a no-confidence motion) reach 124, my 40 votes are with them."
He did not elaborate on what kind of political reforms he would like to see and said he would only support a no-confidence vote provided it did not prove harmful to Iraqis.
Iraq's main Shi'ite, Sunni and Kurdish factions have been locked in a dispute over power since U.S. forces left.
Maliki's opponents have been calling for a vote of no- confidence against the Shi'ite leader, but have so far failed to muster enough support for the motion.
The ruling National Alliance was formed when Maliki's party linked with Sadrists and other Shi'ite groups.
A successful ballot would be the most serious challenge to Maliki in his six years in office, potentially sinking the government and escalating sectarian tensions in a country still pulling back from years of war.
Maliki and Sadr, once foes when the populist cleric's militia battled U.S. and Iraqi security forces, united in 2010 after nine months of political wrangling following an inconclusive vote.
Sadr has criticized Maliki over the political crisis and the premier's opponents say he is amassing power they fear could turn Iraq into a dictatorship like that of Saddam Hussein.
"I once told Nuri al-Maliki: you reached your chair through political blocs," Sadr, who was dressed in clerical black robes and a black headdress, said. "From Shi'ites, Kurds and Sunnis. You've come and hit them later on, this violates the political framework and ethics."
Sadr, the scion of a Shi'ite religious family, said a vote of no confidence against Maliki could not be used as an excuse for government not to deliver services to Iraqi people and said differences between the leaders were long-standing.
Baghdad and Iraqi Kurdistan, an autonomous region in the north with its own government, have old disputes over oil, political autonomy and contested territories.
These spats have intensified in recent months over oil payments and the signing of a deal between the Kurdistan Regional Government and U.S. oil major ExxonMobil.
"Ending the crisis is a difficult thing with these differences and tensions but we try and hope that there will be an end to the crisis," he said.
"I have said already that there should be some concessions by some sides in order to solve the problems. Without these concessions, it is impossible to solve these problems."
(Writing by Serena Chaudhry; Editing by Myra MacDonald and Andrew Osborn)