Ten months after a general election, war-scarred Iraq still has no government, new prime minister or new president, because of disagreement over forming a coalition.

Tensions have been rising since July between the two main Shiite factions, one led by Sadr, the other by the pro-Iran Coordination Framework. Attempts to mediate have so far proved fruitless.

Sadr wants parliament dissolved to pave the way for new elections, but the Coordination Framework wants to set conditions and demands a transitional government before new polls.

A statement from Kadhimi's office said he had called a meeting on Wednesday "to start a serious dialogue; intending to find solutions to the current political crisis".

The Coordination Framework was represented by two former premiers, Nuri al-Maliki and Haider al-Abadi.

Also present were Hadi al-Ameri and Faleh al-Fayyad, senior officials in the Hashed al-Shaabi network of former paramilitaries, now part of the national forces.

Maliki is a longtime foe of Sadr, the influential cleric whose bloc emerged from last October's elections as parliament's biggest, but still far short of a majority.

Sadr supporters have been staging a sit-in outside parliament in Baghdad's high security Green Zone for more than two weeks, and the Coordination Framework began a rival Baghdad protest on Friday.

President Barham Saleh and parliamentary speaker Mohammed al-Halbussi also attended Wednesday's talks, as did officials of the two main Kurdish parties and the UN envoy in Iraq.

A terse press release from the Sadr faction said it was not taking part "in the national dialogue".

Announcing the talks in a statement on Tuesday, Kadhimi's office had said they aimed "to start a profound national dialogue and deliberation; to find solutions to the current political crisis".

Earlier Tuesday, Sadr had backtracked after previously urging his supporters to join a massive rally as the standoff appeared to be getting worse.

He said a "million-man demonstration" planned for Baghdad on Saturday was being postponed indefinitely.