Iraq leaders under mounting pressure to pick PM

In Washington, the Obama administration backed al-Sistani's call for Iraqi leaders to agree on a new government "without delay."

"It's my understanding he was calling for a process that's in line with the constitution, just to do it very quickly," State Department spokeswoman Marie Harf told reporters. "Which we certainly agree with because we think the situation is so serious that they need to move with urgency."

Still, the probability that Iraq's deeply divided political class can mend its differences in the span of days is unlikely.

The United States and other world powers have pressed al-Maliki to reach out to the country's Sunni and Kurdish minorities. Sunnis have long complained of being discriminated against and unfairly targeted by the security forces.

The Islamic State has taken advantage of Sunni discontent to fuel its rise. The group's stunning advance earlier this month, in which it seized Iraq's second largest city Mosul and Saddam Hussein's hometown of Tikrit, was made possible in part because Iraqi security forces melted away in the face of the onslaught.

The United States has already deployed 180 of 300 troops promised by President Barack Obama to assist and advise Iraqi troops. The US also has started flying armed Predator drones over Baghdad to protect US interests in the Iraqi capital, a Pentagon official said Friday. He spoke on condition of anonymity because he was not authorised to discuss the new flights on the record.

On Friday, al-Maliki warned army commanders in televised comments that militants were likely to try to undermine security in the Iraqi capital ahead of Tuesday's parliamentary session.

But he struck an upbeat tone about the military situation, saying the armed forces have regained the initiative and are now on the offensive, citing a Thursday raid on the militant-held city of Tikrit as an example.

Two Iraqi security officials, meanwhile, said several secondhand Sukhoi fighter jets the government purchased from Russia will arrive within days at an air base in southern Iraq. Iraq's air force, which has been decimated over the past two decades, had Sukhoi jets in its fleet before the 2003 US-led invasion.

The officials spoke on condition of anonymity because they were not authorised to speak to media.