Shiite tribal fighters raise their weapons and chant slogans against the al-Qaida-inspired Islamic State of Iraq and the Levant in northwest Baghdad's Shula neighborhood, Iraq, on Monday. The Associated Press

Shiite tribal fighters raise their weapons and chant slogans against the al-Qaida-inspired Islamic State of Iraq and the Levant (ISIL) in the northwest Baghdad's Shula neighborhood, Iraq, Monday. The Associated Press

Iraqis who have fled the violence in their hometown of Mosul reach for fruit during a food distribution at Khazir refugee camp outside of Irbil, 217 miles north of Baghdad, Iraq, on Monday. The Associated Press

Iraqis who have fled the violence in their hometown of Mosul line arrive at Khazir refugee camp outside of Irbil, 217 miles north of Baghdad, Iraq, on Monday. The Associated Press

Iraqi federal policemen watch as Shiite tribal fighters deploy with their weapons in northwest Baghdad's Shula neighborhood in Iraq on Monday. The Associated Press

Demonstrators who support al-Qaida-inspired Islamic State of Iraq and the Levant chant as they carry al-Qaida flags in front of the provincial government headquarters in Mosul, 225 miles northwest of Baghdad, Iraq, on Monday. the Associated Press

A man walks past the remains of burnt vehicles belonging to Iraqi security forces in the northern Iraq city of Mosul on June 13, 2014.

An Iraqi security forces member with his weapon takes position as refugees who fled the violence in Mosul arrive in their vehicles at a camp for displaced people on the outskirts of Arbil in Iraq's Kurdistan region on June 14, 2014. Reuters

Tribal fighters and members of Iraqi security forces carry their weapons take part in a security deployment on the outskirts of Diyala province on Monday. The United States is contemplating talks with its arch-enemy Iran to support the Iraqi government in its battle with Sunni Islamist insurgents.

The amphibious transport dock ship USS Mesa Verde, seen here in a 2011 file photo, entered the Persian Gulf on Monday with 550 Marines on board to support possible U.S. action to help Iraq's Shi'ite-led government combat a Sunni Islamist insurgency. U.S. Navy file photo

A woman volunteer, who joined the Iraqi army to fight against predominantly Sunni militants from the radical Islamic State of Iraq and the Levant (ISIL), flashes a 'V' sign in Baghdad on Sunday.

A boy, who fled from violence in Mosul, washes his head at a camp on the outskirts of Arbil in Iraq's Kurdistan region on Friday.

Children fleeing violence in the Iraqi city of Mosul carry cases of water at a camp on the outskirts of Arbil in Iraq's Kurdistan region on Monday.

A member of the Iraqi security forces guards a checkpoint in Baghdad on Monday.

Iraqi army soldiers stand guard at Tahrir Square in Baghdad on Monday. Sunni militants captured a key northern Iraqi town along the highway to Syria early on Monday, compounding the woes of Iraq’s Shiite-led government a week after it lost a vast swath of territory to the insurgents in the country’s north.

Arshad Salhi, center, head of the Iraqi Turkoman Front, proclaims the formation of a defense system to protect their areas in the oil-rich city of Kirkuk, 180 miles north of Baghdad, on Monday.