Kurdish fighters pushed to retake Iraq's largest dam on Sunday and the United States conducted a second day of air strikes in the area in a drive to reverse gains by Islamic State insurgents who have overrun much of the country's north.
Islamic State militants have seized several towns and oilfields as well as the Mosul Dam in recent weeks, possibly giving them the ability to flood cities or cut off water and electricity supplies.
Asked about a Kurdish push to dislodge the Sunni fundamentalist militants on Sunday, a Kurdish official said the dam had not been retaken but "most of the surrounding area" had been seized.
The United States said it conducted 14 air strikes on Sunday against Islamic State fighters near the dam.
U.S. Central Command said the latest strikes destroyed three armed vehicles, a vehicle-mounted anti-aircraft and an emplacement of the Islamic State as well as one of the militants' checkpoints. The strikes followed nine U.S. air strikes on Saturday near the dam and the Kurdish capital, Arbil.
The White House said on Sunday that President Barack Obama had informed Congress he authorized U.S. air strikes to help retake control of the dam.
"The failure of the Mosul Dam could threaten the lives of large numbers of civilians, threaten U.S. personnel and facilities - including the U.S. Embassy in Baghdad - and prevent the Iraqi government from providing critical services to the Iraqi populace," the White House said in a statement.
The U.S. air strike campaign against the Islamic State militants began earlier this month in the first direct U.S. military action in Iraq since the end of 2011, when Washington completed the withdrawal of its troops from the country.
Islamic State militants have told residents in the area of the Mosul Dam to leave, according to an engineer who works at the site.
The engineer said the militants told him they were planting roadside bombs along roads leading in and out of the facility, possibly in fear of an attack by Kurdish fighters.
U.S. officials said last week the U.S. government was directly supplying weapons to Kurdish peshmerga fighters.
Witnesses said Kurdish forces had recaptured the mainly Christian towns of Batmaiya and Telasqaf, 30 km (18 miles) from Mosul, the closest they have come to the city since Islamic State insurgents drove government forces out in June.
The insurgents have also tightened their security checkpoints in Mosul, conducting more intensive inspections of vehicles and identification cards, witnesses