(CNN) -- U.S. airstrikes helped Kurdish and Iraqi forces take control of Mosul Dam on Monday, fighting back ISIS militants who had seized the dam, President Obama told reporters.

The stakes were huge for the millions of Iraqis who live downstream from the dam, the largest in the country.

"If that dam was breached it could have proven catastrophic, with floods that would have threatened the lives of thousands of civilians and endangered our embassy compound in Baghdad," the President said.

"The U.S. military used fighters, bombers, attack and unmanned aircraft to conduct35 strikes, " said Pentagon spokesman Rear Adm. John Kirby. "We destroyed over 90 targets including a range of vehicles, equipment and fighting positions," he said.

Now that the dam is cleared of ISIS militants, Iraqi forces are moving to grow their area of control, the Pentagon said.

"This operation demonstrates that Iraqi and Kurdish forces are capable of working together and taking the fight to ISIS," Obama said. "If they continue to do so, they will have the strong support of the United States of America."

Built in the early 1980s under former Iraqi dictator Saddam Hussein, the dam sits on the Tigris River about 50 kilometers (30 miles) north of the city of Mosul. It serves as a key source of electricity, irrigation and flood protection.

When ISIS militants seized the dam this month, many feared it could be used as a weapon.

Kurdish Peshmerga fighters and Iraqi troops have retaken Mosul dam from Islamic State (IS) militants, US President Barack Obama has said.

Mr Obama said the US helped in the operation. Air strikes targeted IS around the dam, Iraq's largest.

He said the move was a "major step forward", and the US had begun a long-term strategy to defeat the militants.

The statement followed Iraqi claims that the dam had been "fully cleansed", but IS said it was still in control.

Separately, Pope Francis said action to stop IS attacking religious minorities should be agreed by the UN.

He said intervention should not be carried out by "one nation alone".

BBC Rome correspondent Alan Johnston says that up until now the Pope has taken a resolutely pacifist view, but on this occasion he seemed a little less emphatic in his opposition to a more muscular approach.

Christians have been among religious groups persecuted by IS since the militants captured a swathe of north-western Iraq.

The Pope said he was considering a visit to the region to show solidarity with its Christians.

At the scene: Paul Wood, BBC News, near the Mosul Dam

Wartawan BBC meliput di Dam Mosul

We drove towards the dam, following a path cleared by the Kurdish forces. Until a few days ago, the road, and the villages either side were in the hands of Islamic State. There were several burnt-out vehicles and blackened buildings, evidence of the fighting, and that the jihadists did not leave easily.

We reached a Kurdish forward artillery position. The jihadists were just two miles (3km) away from the battery, the soldiers said. They fired a Grad rocket launcher to push them back still further.

A plume of smoke of the horizon was a village burning, set alight by the jihadists as they retreated, a Kurdish special forces officer told me. He was confident they had Islamic State was on the run. Shortly after he told us this, a mortar shell came in, landing about 50m (160ft) away in the soft earth.

"Don't worry, they're running out of ammunition," said the officer. Five minutes later, another round landed. We decided to leave.

Still, the Kurds are making progress - assisted by American air power overhead. The fight for the city of Mosul itself will, of course, be much, much harder. And the Mosul dam is just one of many battlefronts against Islamic State throughout Iraq.