"We have reluctantly accepted the requests of our brothers and sisters, representatives of the Sadr bloc, to resign," parliament's speaker Mohammed al-Halbussi said on Twitter after receiving resignation letters from the 73 lawmakers.

Sadr on Thursday had urged the MPs from his bloc -- the biggest in parliament -- to ready resignation papers, in a bid, he said, to break the parliamentary logjam and create space for the establishment of a new government.

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.

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.

Parliamentary services were not available on Sunday evening for comment on the constitutional implications of the Sadr bloc's move.

But Iraqi political scientist Hamzeh Haddad said that "parliament still needs to ratify" the resignations "with an absolute majority" for them to take effect.

Parliamentary holidays began on Thursday and MPs are not scheduled to return until August.

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

While Sadr counts on the direct loyalty of 73 lawmakers, his wider bloc also includes Sunni lawmakers from the party of parliamentary speaker Halbussi 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.

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

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 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 had said Thursday in a televised statement.