Parliament in Baghdad has been in turmoil since October's general election, and intense negotiations among political factions have failed to forge a majority in support of a new prime minister to succeed Mustafa al-Kadhemi.

The two Shiite groupings -- a coalition led by Sadr, and its powerful rival, the Coordination Framework -- each claim to hold a parliamentary majority, and with it the right to appoint the prime minister.

Iraqi lawmakers have already exceeded all deadlines for setting up a new government set down in the constitution, prolonging the war-scarred country's political crisis.

"If the survival of the Sadrist bloc is an obstacle to the formation of the government, then all representatives of the bloc are ready to resign from parliament," Sadr said in a televised statement.

Sadr called on his lawmakers to "write their resignation", warning that "they won't disobey me".

"Iraq needs a government backed by a majority that serves the people," Sadr said.

The 47-year-old cleric once led an anti-US militia following the 2003 invasion to topple Saddam Hussein, and he maintains a large and dedicated following.

Sadr has said he wants all Shiite forces to be involved in a "consensus government".

While Sadr counts on the direct loyalty of 73 lawmakers, his wider bloc also includes Sunni lawmakers from the party of parliamentary speaker Mohammed Halbusi and the Kurdistan Democratic Party (KDP).

But the grand total of Sadr's bloc of 155 still falls short of the absolute majority needed in the 329-member parliament.

Sadr's move puts the onus for forming a government on the 83 lawmakers of the rival Coordination Framework, which draws lawmakers from former premier Nuri al-Maliki's party and the pro-Iran Fatah Alliance, the political arm of the Shiite-led former paramilitary group Hashed al-Shaabi.

Lawmakers have already failed three times to elect a new national president, the first key stage before naming a prime minister and the subsequent establishment of a government.

If the parliamentary impasse cannot be broken, new elections could follow -- but that would itself require lawmakers to agree on dissolving parliament.