Sadr proved influential as Iraq tried to end a lingering political stalemate last year. Iraqi Prime Minister Nouri al-Maliki was able to get enough support for a second term following a November visit to Iran, where the anti-American Sadr was pursing cleric studies before returning to Iraq early this year.
Sadrists, members of the party loyal to the cleric, said they might revoke their support for Maliki because of his failures, Iraqi satellite channel al-Sumaria reports. Members suggested they might throw their weight behind Iyad Allawi, a former interim prime minister who challenged Maliki in the latest elections.
Iraqi protesters complained last week that the government wasn't meeting their basic needs.
Sadrists at one point during the political turmoil last year were avid supporters of Allawi, who won a national election but couldn't get the support needed to lead the country.
Allawi, meanwhile, said he won't lead a strategic council tasked with checking the powers of the prime minister because of ongoing disputes over the Kurdish region of Iraq.
His recommendation to chair the council was seen as a concession for losing the leadership position to Maliki.