In the latest political turmoil to strike the oil-rich but war-scarred country, Sadr called for a "revolutionary and peaceful process, then early democratic elections after a dissolution of parliament".

Nearly 10 months on from the last elections, the country still has no government and no new prime minister or president after repeated squabbles between factions over forming a coalition.

Sadr, who once led an anti-US militia and who has millions of devoted followers, noted in a televised speech that he also had "no interest" in negotiating with his rivals.

"Don't believe the rumours that I don't want dialogue," Sadr said Wednesday.

"But we have already tried and experienced dialogue with them," he added. "It has brought nothing to us and to the nation -- only ruin and corruption."

His speech came as his supporters occupied parliament for a fifth consecutive day, in protest at a nomination for prime minister by a rival Shiite faction, the Iran-backed Coordination Framework.

Surrounding parliament, Sadr supporters have set up an encampment with tents and food stalls.

Outgoing prime minister Mustafa al-Kadhemi has called for a "national dialogue" in a bid to bring all sides together to talk, and on Wednesday he spoke with President Barham Saleh.

Both men stressed the importance of "guaranteeing security and stability" in the country, according to the Iraqi News Agency.

Earlier on Wednesday, the United Nations mission in Iraq called on leaders to put their country first and end the long-running power struggle.

"Meaningful dialogue among all Iraqi parties is now more urgent than ever, as recent events have demonstrated the rapid risk of escalation in this tense political climate," the UN mission warned.