MOSUL/BAGHDAD (Reuters) - The United States is contemplating talks with its arch enemy Iran to support the Iraqi government in its battle with Sunni Islamist insurgents who routed Baghdad's army and seized the north of the country in the past week.
The stunning onslaught by militants from the Islamic State of Iraq and the Levant threatens to dismember Iraq and unleash all-out sectarian warfare across a crescent of the Middle East, with no regard for national borders that the fighters reject.
Joint action between the United States and Iran to help prop up the government of their mutual ally Nuri al-Maliki, the Iraqi prime minister, would be a major breakthrough after hostility dating to Iran's 1979 revolution, and demonstrates the degree of alarm raised by the lightning insurgent advance.
The ISIL fighters captured the mainly ethnic Turkmen city of Tal Afar in northwestern Iraq overnight after heavy fighting on Sunday, solidifying their grip on the north.
"The city was overrun by militants. Severe fighting took place, and many people were killed. Shi'ite families have fled to the west and Sunni families have fled to the east," said a city official who asked not to be identified.
Tal Afar is a short drive west from Mosul, the north's main city, which ISIL seized last week at the start of a drive that has plunged the country into the worst crisis since U.S. troops withdrew in 2011.
ISIL, seeking a Sunni caliphate in Iraq and Syria, is also fighting Syria's Iranian-backed government. It has support among some in Iraq's Sunni minority who see the Shi'ite Maliki as both a pawn of Iran and of the United States, whose forces ended decades of Sunni dominance by toppling Saddam Hussein in 2003.
A senior U.S. official, speaking on condition of anonymity, said on Sunday that Washington was considering making contact with Iran to find ways to aid the Baghdad government. Publicly, the White House said no such contacts had yet taken place.
The U.S. overture came a day after Iran's President Hassan Rouhani, a relative moderate elected last year, said Tehran would consider working with the United States in Iraq if it saw that Washington was willing to confront "terrorist groups".
U.S. President Barack Obama has ruled out sending troops back into Iraq although he says he is weighing other military options, such as air strikes. A U.S. aircraft carrier has sailed into the Gulf.
The only U.S. military contingent on the ground are the security staff at the U.S. embassy. Washington said on Sunday it was evacuating some diplomatic staff and sending about 100 extra marines and other personnel to help safeguard the facilities.
The sprawling fortified compound on the banks of the Tigris is the largest and most expensive diplomatic mission ever built, a vestige of the days when 170,000 U.S. troops fought to put down a civil war and mass sectarian cleansing that followed the 2003 U.S. invasion that toppled dictator Saddam Hussein.
Iraqis now face the prospect of a replay of that extreme violence, but this time without American forces to intervene.
The prospect of cooperation between the United States and Iran shows how dramatically the ISIL advance has redrawn the map of the Middle East in a matter of days.
Rouhani has presided over a gradual thaw with the West, including secret talks with Washington that led to a breakthrough preliminary deal last year to ease sanctions in return for curbs on Iran's nuclear program. But open cooperation against a mutual threat would be unprecedented.
Iraq is the only country closely allied to both the United States and Iran, but tentative past efforts by Tehran and Washington to cooperate there were fruitless. Tehran has longstanding ties to Maliki and the Shi'ite political parties that U.S.-backed elections brought to power after Saddam's fall.
Iran blames the United States and its Gulf Arab allies for stoking Sunni militancy in the region by backing the uprising against its ally Bashar al-Assad in Syria, where ISIL emerged as one of a dominant Sunni rebel group in a three year civil war.
Asked if Iran would now work with the United States against ISIL, Rouhani told a news conference on Saturday: "We can think about it, if we see America starts confronting the terrorist groups in Iraq or elsewhere.
"Where did ISIL come from? Who is funding this terrorist group? We had warned everyone, including the West, about the danger of backing such a terrorist and reckless group," he said.
ISIL fighters began their assault last week by capturing Mosul. They swept through other Sunni cities in the Tigris valley north of Baghdad, including Saddam's hometown Tikrit.
Tal Afar, the city captured on Sunday, had been defended by an unit of Iraq's security forces commanded by a Shi'ite major general, Abu Walid, whose men were among the few army holdouts in the province around Mosul not to flee the rapid ISIL advance.
Most of the inhabitants of Tal Afar are members of the Turkmen ethnic group. Turkey has expressed concern.
ISIL fighters appear to have halted their advance in towns along the Tigris an hour's drive north of the capital. They also hold most of the Euphrates valley to the west, which they captured at the start of the year, bringing them to the gates of the city of 7 million people.
Shi'ites, who form the majority in Iraq and are based mainly in the south, have rallied to defend the country, with thousands of volunteers turning out to join the security forces after a mobilization call by the top Shi'ite cleric.
Baghdad itself is divided between Sunni and Shi'ite neighborhoods and suffered intense street fighting in 2006-2007. Peace never quite returned and districts are still surrounded by barbed wire and concrete blast walls.
ISIL fighters aim to establish a state on both sides of the Syria-Iraqi frontier based on strict medieval Sunni Muslim precepts. The group, which fought against the U.S. occupation as al Qaeda's Iraq branch, broke away from al Qaeda after joining the civil war in Syria and now says the jihadist movement founded by Osama bin Laden is no longer radical enough.
Their advance in Iraq has been assisted by other Sunni Muslim armed groups, alienated by what many Sunnis believe is repression from Maliki's Shi'ite-led government.
The government's collapse in the north has also allowed forces of the Kurdish autonomous region to advance, seizing the city of Kirkuk and rural areas with vast oil reserves.
Residents in Tal Afar said Shi'ite police and troops rocketed Sunni neighborhoods before the ISIL forces moved in and finally captured the city. A member of Maliki's security committee told Reuters that government forces had attacked ISIL positions on the outskirts of the city with helicopters.
"The situation is disastrous in Tal Afar. There is crazy fighting and most families are trapped inside houses. They can’t leave town," a local official said on Sunday before the city was overrun. "If the fighting continues, a mass killing among civilians could result."
In years of fighting on both sides of the frontier, ISIL has gained a reputation for shocking brutality. It considers Shi'ites to be heretics deserving of death and its bombers have been killing hundreds of Iraqi civilians each month.
A series of pictures distributed on a purported ISIL Twitter account appeared to show gunmen from the Islamist group shooting dozens of men, unarmed and lying prone on the ground.
Captions accompanying the pictures said they showed hundreds of army deserters captured as they tried to flee the fighting. They were shown being transported in the back of trucks, led to an open field, laid down in rows and shot by several masked gunmen. In several pictures, the black ISIL flag can be seen.
Most of the captured men wore civilian clothes, although one picture showed two men in military camouflage trousers, one of them half covered by a pair of ordinary trousers.
"This is the fate of the Shi'ites which Nuri brought to fight the Sunnis," a caption to one of the pictures reads.