Iraqi Prime Minister Nuri al-Maliki took a major step toward staying in power yesterday when a leading Shiite cleric said he would not block him, as an arch-rival warned of civil war.

A spokesman for radical, anti-US cleric Moqtada al-Sadr told AFP the movement would drop a veto against Maliki seeking a new term as premier as long as he met its condition that around 2,000 Sadrist prisoners be freed.

Sadr has previously opposed the incumbent keeping his job and several public statements delivered by spokesmen or senior aides have been highly critical of him.

But yesterday's conciliatory statement, which followed discussions between the two sides in the past 48 hours, would eliminate Maliki's biggest hurdle.

"If he will give us sufficient guarantees to end our reluctance, especially concerning the arrests of Sadrists, then we will not block his candidacy for a second term," spokesman Saleh al-Obeidi told AFP from the Shiite holy city of Najaf in southern Iraq.

But he added: "Maliki has not yet succeeded in giving us assurances about these conditions."

The Sadrist movement is part of a recently formed Shiite coalition that includes Maliki's State of Law Alliance, but the cleric's political bloc had long despised the premier, who had authorised an assault on its armed wing, the Mahdi Army, in 2008.

Sadr, who is in self-imposed exile in Iran, in an interview with Al-Jazeera television after the election, said he had "tried not to have a veto against anyone, but the masses had a veto against Maliki."

The new Sadrist stance was welcomed by Maliki adviser Ali Mussawi, who said it "paved the way to agreement with other blocs to solve the problem of forming a government."

Turning to the Sadrist call for a release of prisoners, Mussawi said "committees have been formed... to release innocent prisoners as soon as possible."

Maliki could not intervene in the case of prisoners who have been formally charged with an offence, he said.

The latest announcement came as former premier Iyad Allawi, who narrowly beat Maliki in a March 7 general election, said if a "new wave" of violence sweeping Iraq were to continue, then the country was headed for civil war.

"After the elections we have seen a new wave of sectarianism which is very dangerous and we have indications that we are heading towards a new peak," Allawi told the Spanish newspaper El Mundo.

"We are just at the beginning, but if the violence continues we are heading towards civil war." Allawi's Iraqiya bloc won 91 seats in the election, two more than State of Law, with the Iraqi National Alliance, of which the Sadrists are a part, coming in third with 70 seats.