Eis het ontslag van Jozias van Aartsen

Washington (CNN) -- [Breaking news update, posted at 11:37 a.m. ET]

U.S. airstrikes have "successfully destroyed arms and equipment" that terrorists with ISIS could have used against the Kurdish regional capital of Irbil in Iraq, U.S. President Barack Obama said Saturday.

"We feel confident" that military efforts can prevent ISIS from slaughtering people on Mount Sinjar, where ISIS has been killing many members of the Yazidi minority, Obama said in remarks at the White House.

He declined to give a timetable for U.S. airstrikes and humanitarian air drops in Iraq. "Wherever and whenever (U.S.) personnel are facilities are threatened, it is my obligation ... to make sure they're protected," he said.

The Iraqi government and military will need to take a series of steps to improve the security situation, Obama said. "I don't think we're going to solve this problem in weeks. I think this is going to take some time."

There's a lesson in this situation for Afghanistan, the president said: If leadership wants a new government to work, then people of different factions and ethnicities have "got to accommodate each other."

After a reporter asked Obama if he felt ISIS had been underestimated, Obama said the advance of the Sunni Islamic extremists has been "more rapid" than intelligence officials and policymakers in and outside Iraq had predicted.

But he said ISIS' advance was made possible in part by the lack of an inclusive and functioning Iraqi government -- a dig at the Shiite-led government that he says has alienated Sunnis in recent years.

This was illustrated, he said, by Iraqi security forces' capitulation to ISIS in northern Iraq earlier this year. The government forces, "when they (were) far away from Baghdad, did not have the incentive or the capacity to ... hold (their) ground against an aggressive adversary," Obama said.

"That's one more reason why" the formation of a functioning Iraqi government is so important, he said.

While the U.S. can assist Iraqi security forces in fighting ISIS with airstrikes, ultimately it's up to Iraqis to secure their country, the president said. That will take an inclusive government, he said. "All Iraqi communities need to unite to defend their country," Obama said.

Obama said he spoke with French President Francois Hollande and British Prime Minister David Cameron about the situation in Iraq, and that both have agreed to join the United States in providing humanitarian assistance to Iraqis endangered by ISIS.

The British government will contribute aid worth 8 million pounds ($13.4 million), and its air force will start air-dropping supplies in northern Iraq soon, particularly for the Yazidis trapped on the mountain, UK Foreign Secretary Philip Hammond said Saturday.

[Previous version, published at 6:01 a.m. ET]

U.S. fighter jets, drones target ISIS fighters, convoys in Iraq

(CNN) U.S. fighter jets and drones repeatedly bombed Sunni Islamic extremists in northern Iraq, targeting what officials described as ISIS artillery units and convoys advancing on the Kurdish regional capital of Irbil.

The airstrikes Friday ramped up America's involvement in Iraq where ISIS, which calls itself the Islamic State, is seizing control of towns and key infrastructure in an advance that has forced hundreds of thousands to run for their lives.

News of the second round of U.S. airstrikes came just after the governor of Irbil told CNN that ISIS may be as close as 30 kilometers (just over 18 miles) from the city of more than a million people.

The operation began hours after President Barack Obama authorized "targeted airstrikes," saying in a televised address late Thursday that the United States had an obligation to protect its personnel in Iraq and prevent a potential genocide of minority groups by ISIS.

Obama said there will be no buildup of U.S. combat troops in Iraq. "As commander in chief, I will not allow the United States to be dragged into fighting another war in Iraq," the President said.

During his weekly radio address Saturday, the President reiterated his stance.

"American combat troops will not be returning to fight in Iraq, because there's no American military solution to the larger crisis there," Obama said.

Hitting ISIS

Two U.S. F/A 18 fighters first struck an ISIS artillery unit outside of Irbil, dropping two 500-pound laser-guided bombs about 6:45 a.m. ET Friday, Pentagon spokesman Navy Rear Adm. John Kirby said.

Later, a drone targeted an ISIS mortar position, Kirby said. When ISIS fighters returned to the site a short time later, the drone struck the target again, he said.

That was followed a short time later by a second round of airstrikes, carried out by four U.S. fighter jets, which targeted an ISIS convoy of seven vehicles and another mortar position, Kirby said.

The F/A 18s made two passes, dropping a total of eight laser-guided bombs, he said.

The United States has hundreds of military personnel in Iraq, including advisers sent in recent weeks to coordinate with Iraqi and Kurdish military officials in response to the ISIS rampage. The USS George H.W. Bush and other Navy ships also are in the region.

Airstrikes are crucial because ISIS fighters are well-armed and are outgunning the Kurdish forces, thanks to the weapons the militants seized from the Iraqi military in Mosul, Irbil Gov. Nawzad Hadi said.

Map: Where is ISIS?

Militants using U.S.-made weapons

Even as the airstrikes were under way, there was news that ISIS militants captured Iraq's largest hydroelectric dam, just north of Mosul, Iraq's second-largest city. According to a senior Kurdish official, the militant fighters have been using U.S.-made weapons seized during fighting from the Iraqi army, including M1 Abrams tanks.

There had been conflicting reports about who controlled the dam on the Tigris River, with heavy fighting under way between ISIS fighters and Kurdish forces, known as Peshmerga. U.S. officials have warned that a failure of the dam would be catastrophic, resulting in flooding all the way to Baghdad.

In other fighting, an Iraqi airstrike killed 45 ISIS fighters and injured 60 Friday in the northern town of Sinjar, the country's state-run National Media Center said.

U.S. flights prohibited

In other signs of a growing regional conflict: The Federal Aviation Administration issued a notice prohibiting U.S. airlines from flying through Iraqi airspace "due to the hazardous situation created by the armed conflict."

The developments showed that the lightning advance by ISIS fighters across northern Iraq this year has become a battle for the nation's future and overall stability in a part of the world wracked for decades by periodic war.

Kurdish pleas

In announcing his airstrike decision Thursday night, Obama said the militants would get hit "should they move towards the city."

Kurdish leaders have been pleading for the United States or NATO to buttress their forces against ISIS from the air. The President seems to have heard their appeal.

"We do whatever is necessary to protect our people," Obama said, adding, "We support our allies when they're in danger."

Before Obama announced the airstrikes, two U.S. military cargo planes airdropped 5,300 gallons of water and 8,000 meals onto Mount Sinjar, where some Yazidi children had died from dehydration.

A Predator drone flying overhead indicates the Yazidis have 63 of the 72 pallets dropped with aid supplies. It's not clear if the other pallets missed the drop zone or are in ISIS hands.

ISIS overran Sinjar last weekend, forcing tens of thousands of Yazidis to flee into surrounding mountains without food, water or shelter, and prompting concerns of a potential genocide. The Yazidis are of Kurdish descent, and their religion is considered a pre-Islamic sect that draws from Christianity, Judaism and Zoroastrianism.

"The thousands—perhaps tens of thousands—of Iraqi men, women and children who fled to that mountain were starving and dying of thirst," Obama said during his weekly address. "The food and water we airdropped will help them survive. I've also approved targeted American airstrikes to help Iraqi forces break the siege and rescue these families. Earlier this week, one anguished Iraqi in this area cried to the world, 'There is no one coming to help.' Today, America is helping."

Beheadings

ISIS has executed people who don't share their fanatical interpretation of Sunni Islam and posted videos of their killings to the Internet. "Convert to Islam or die" is the militants' ultimatum to those captured.

Its members have also have beheaded victims and placed their heads on spikes to strike terror in the population, a senior administration official said.

CNN's Barbara Starr and Tom Cohen reported from Washington and Chelsea J. Carter reported and wrote from Atlanta. CNN's Ivan Watson, Catherine E. Shoichet, Ben Brumfield, Jim Sciutto, Niki Cook, Elise Labott, Mohammed Tawfeeq, Jim Acosta, Jamie Crawford, Mohammed Tawfeeq and Hamdi Alkhshali contributed to this report.