Since the aftermath of the US-led invasion of 2003 that toppled longtime dictator Saddam Hussein, Iraq has been governed under a sectarian power-sharing system.

But since elections in October last year, political deadlock has left the country without a new government, prime minister or president, due to disagreement between factions over forming a coalition.

Sadr and his supporters have been calling for parliament to be dissolved and for new elections, but on Saturday he said doing so was not "so important".

Instead, it is "more important" that "all parties and figures who have been part of the political process from the American occupation in 2003 until now no longer participate", Sadr said on Twitter.

"That includes the Sadrist movement," he added.

"I am ready to sign an agreement to this effect within 72 hours," he said, warning that without such a move, "there would no longer be anymore room for reforms."

He did not indicate who he expected would lead a future government.

Sadr's supporters have for weeks been staging a sit-in outside Iraq's parliament, after initially storming the legislature's interior, to press for their demands.

On Tuesday, they also pitched tents outside the judicial body's headquarters in Baghdad for several hours.

Sadr's rivals in the pro-Iran Coordination Framework want a new head of government to be appointed before any new polls are held.

Caretaker Prime Minister Mustafa al-Kadhemi earlier this month convened crisis talks with party leaders, but they were boycotted by the Sadrists.