Iraq's top Shiite cleric yesterday urged all of its people to unite and expel Sunni Muslim insurgents, as Shiite Prime Minister Nouri al-Maliki came under growing pressure at home and abroad.
The call came after US President Barack Obama stopped short of acceding to Maliki's appeal for air strikes on the Islamic State of Iraq and the Levant (ISIL), prompting Iran to charge that Washington lacked the "will" to fight terror.
A swift ISIL-led offensive has overrun swathes of northern and central Iraq, threatening the United States's already damaged legacy in the country.
Grand Ayatollah Ali al-Sistani, a revered cleric whose stature dwarfs that of any other figure among the Shiite majority, called for Iraqis to band together before it was too late.
If ISIL was not "fought and expelled from Iraq, everyone will regret it tomorrow, when regret has no meaning", his spokesman announced on his behalf.
The reclusive Sistani also said Iraq's next government must be "effective" and avoid "past mistakes", an apparent rebuke to Maliki, premier since 2006.
His remarks came after several senior US figures pushed Maliki to work with Iraq's Sunni Arab and Kurdish minorities.
Obama said on Thursday that Maliki's actions could dictate the country's fate, amid a growing feeling in Washington that the Iraqi leader would do best by moving on.
Former US ambassador to Baghdad James Jeffrey said there has been a "definite uptick" in Washington's criticism of Maliki.
"Everybody is a bit at fault in Iraq on the sectarian thing, but Maliki over time did become more" sectarian, said Jeffrey.
"He just isn't the solution to a unified Iraq."
Obama, who based his political career on ending the costly eight-year US intervention in Iraq, has insisted the troubled country is not slipping back into the morass.
But he has offered as many as 300 military advisers and left open the possibility of "targeted and precise military action if and when we determine that the situation on the ground requires it".
Washington has already positioned an aircraft carrier in the Gulf and is flying manned and unmanned surveillance flights over Iraq. It is also still considering drone strikes.
The latest offer was the most concrete action yet announced by Washington. But it fell short of Iraq's request for air strikes and drew derision from Tehran, which has offered its cooperation despite decades of enmity.
"Obama's comments show the White House lacks serious will in fighting terrorism in Iraq and the region," Iran's Deputy Foreign Minister Hossein Amir Abdollahian said.
A senior Iraqi army officer said Iraq needed US help.
"We need American support to stop terrorism and eliminate it ... especially through air strikes against specific targets," the lieutenant general said, asking not to be identified.
Meanwhile, UN aid agencies said they were rushing supplies to Iraq to help more than one million people driven from their homes.
About 500,000 people had been displaced in the western Anbar province since the start of the year, with a similar number fleeing Mosul when it fell to the ISIL last week, the UN said.