ALQOSH, Iraq — Seizing on the momentum of focused US airstrikes in recent days, Kurdish forces moved to retake the strategic Mosul Dam on Sunday night, in their most significant challenge yet to the Sunni militants’ advance in northern Iraq.
In the past two days, US military forces have conducted 30 airstrikes across Iraq, officials said, with many of them focused around the dam, which militants captured after routing the Kurdish forces 10 days ago.
The White House said Sunday that President Obama has notified Congress the United States is expanding its air campaign in Iraq with attacks aimed at helping Iraqi forces regain control of the dam, the Associated Press reported. Obama said the widened mission would be limited in duration and scope.
The White House said ‘‘the mission is consistent with the president’s directive that the US military protect US personnel and facilities in Iraq, since the failure of the Mosul Dam could threaten the lives of large numbers of civilians and threaten US personnel and facilities, including the US Embassy in Baghdad.’’
The latest round of US airstrikes in Iraq against the Islamic State extremist group includes the first reported use of land-based bombers in the military campaign, the AP said.
On Sunday alone, the US air assaults hit 10 armed vehicles, seven Humvees, two armored personnel carriers, and one checkpoint belonging to the Islamic State, according to the US Central Command.
On Saturday, the United States carried out nine airstrikes near the dam, destroying four armored personnel carriers, seven armed vehicles, two Humvees, and another armored vehicle, the command said.
The dam on the Tigris, about 30 miles from Mosul, is the largest in Iraq and supplies electricity to a large part of the country. It also is a control point for the water supply for a large area.
After the dam fell to the insurgents this month, officials worried that if it failed, a 65-foot wave of water could be released over northern Iraq. But rather than use the dam as a weapon against residents of the region, the militants continued to produce electricity and maintain the site.
As of late Sunday, Kurdish government officials said fighting around the dam complex, Iraq’s largest, was continuing, despite early reports that the site had been retaken.
“We do not control the entire dam yet,” Fuad Hussein, a spokesman for Massoud Barzani, the president of the Kurdistan region of Iraq, said in a televised statement.
The air campaign has seemed to check the militants’ move against the semiautonomous Kurdish region, an offensive that sent tens of thousands of refugees fleeing for safety and at one point threatened the Kurdish capital, Irbil.
By hammering the militants with warplanes and drones, the Americans have severely curtailed the freedom of movement enjoyed by the fighters of the Islamic State group.
It remains to be seen how the Kurdish forces, known as the peshmerga, may fare if the air support is halted. Having lost significant ground during the Islamic State fighters’ sudden advance this month, Kurdish forces have shown that they may not be able to go it alone.
The forces pushing into the Mosul Dam area are believed to include the Iraqi Special Forces, making the operation a hybrid of US, Kurdish, and Iraqi commands.
Kurdish officials acknowledge that the airstrikes have been vital to their recent success. For their part, peshmerga officials have complained bitterly about inferior arms compared with those used by the Islamic State militants, who have claimed powerful US munitions abandoned on the battlefield by the Iraqi military.
“The aircraft have handicapped” the Islamic State forces. “They cannot move easily,” said Hariam Agha, a local commander for the Kurdish forces in Dohuk. “They killed a lot of their fighters.”
Since Saturday, 13 militants had been killed in airstrikes and 46 had been wounded, medical officials in the area said.
According to Kurdish officials, Islamic State fighters appeared to be falling back on several fronts, as peshmerga forces approached both the dam and the city of Mosul, which is the capital of Nineveh province.
In their retreat, they have left mines to slow the progress of Kurdish and Iraqi government forces. The Kurdish advance appeared to have been halted Sunday afternoon, as local fighters and officials said they were awaiting teams to clear the way to the dam.
Still, in Alqosh, at the military base from where the operations to retake the dam originated, there was a decidedly optimistic attitude among the government fighters. Several offered to speak to reporters visiting the area but only if they were not identified because they were not authorized to comment publicly.
The soldiers boasted that the Islamic State fighters were not retreating from the dam and spoke of an imminent victory there as military vehicles passed in and out of the checkpoint area.