Arguing that the U.S. could not ignore the humanitarian crisis in Iraq, President Obama Thursday night announced that he had authorized limited air strikes, one of the boldest military moves of his presidency.

The decision marks a reversal of Obama's long-stated goal of ending U.S. military intervention in Iraq, as well as his current, more supervisory approach to the violent turmoil in the country prompted by Islamic insurgents' siege of large swaths of the country.

Speaking about the continued necessity for American leadership in the world under specific scenarios, he said ISIS threats of genocide against ethnic and religious minorities trapped on a mountain in Iraq and threats to U.S. troops and personnel in the region spurred him to act.

"When we face a situation like we do on that mountain -- with innocent people facing the prospect of violence on a horrific scale, when we have a mandate to help -- in this case, a request from the Iraqi government -- and when we have the unique capabilities to help avert a massacre, then I believe the United States of America cannot turn a blind eye," Obama said in a televised statement Thursday night in the White House's East Room.

"We can act, carefully and responsibly, to prevent a potential act of genocide," he added.

The president made the decision after nearly round-the-clock meetings over the last 24 hours with his national security team on how to handle the intensifying humanitarian crisis in Northern Iraq where the Islamic State of Iraq and Syria has trapped tens of thousands of people on a mountain without food and water.

Obama acknowledged his resistance to taking military action during international crises and said he takes no decision more seriously.

"I have been careful to resist calls to turn time and again to our military because America has other tools in our arsenal than our military. We can also lead with the power of our diplomacy, our economy, and our ideals," he said.

"But when the lives of American citizens are at risk, we will take action. That’s my responsibility as commander in chief, and when thousands of civilians are faced with the danger of being wiped out, we will take action."

In an appeal to the war-weary American public's sense of morality and justice, Obama said intervening in Iraq right now is "our responsibility as Americans," adding that said standing up to militants threatening genocide is a "hallmark of America."

"That's who we are," he said.

Obama recalled how earlier in the week, one Iraqi in the area cried out to the world, "There is no one coming to help."

"Well, today America is coming to help," he said, noting that U.S. officials would be consulting with other countries and the United Nations, which has called for action to address the humanitarian crisis.

A senior administration official later differentiated Obama's decision to authorize military action in Iraq from his decision last fall not to follow-through on his red-line threat to Syria.

"We have not seen a viable military option in Syria that has been as clear and as distinct as we have today [in Iraq]," the official said.

Any airstrikes would be targeted and limited and unlikely to begin Thursday night, although that expectation could change with circumstances on the ground, a U.S. official cautioned.

Obama said he has given the green-light to the Pentagon for the limited, targeted bombing if top military officials monitoring the shifting situation on the ground believe ISIS continues to pose a serious threat to people in the northern Kurdish-controlled region or if militants threaten U.S. servicemen and personnel in Irbil, according to a U.S. official.

Still, the president’s authorization of any airstrikes in Iraq is abrupt departure from his goal of preventing further U.S. military intervention in the country after ending the war there and removing all troops at the end of 2011. Obama was swept into office in 2008 in part because of his promises to end the wars in Iraq and Afghanistan and limit U.S. military intervention abroad.

Obama had delayed any direct military action in the Iraqi crisis, when ISIS first began seizing some of the country’s major cities. But the developments over the last few days, when 40,000 people became trapped on Mt. Sinjar and were dying in the heat, pushed Obama into action.

Over the last two months, Obama has sent 750 American military advisers and personnel to help advise the Iraqi military and Kurdish forces beat back ISIS and secure the U.S. embassy and the airport there.

At the time, Obama said there was ultimately no military solution, and it would be up to the Iraqi government to determine whether it could empower the Sunnis who were disenfranchised under Prime Minister Nouri Maliki’s government.

But Obama made clear that he could authorize military action if ISIS continued its murderous march across Iraq and if the militants threatened U.S. servicemen and personnel.

On Thursday night, Obama again said only political reconciliation can bring a "lasting solution" to the Iraq's problems.

"However, we can and should support moderate forces who can bring stability to Iraq," he said. "So even as we carry out these two missions, we will continue to pursue a broader strategy that empowers Iraqis to confront this crisis."

Irbil, a city of 1.5 million, is the capital of the Iraq’s Kurdish region and home to a U.S. Joint Special Operations Command, which has expanded rapidly in recent weeks as the U.S. considered whether to engage in war against ISIS after it seized control of nearly half of Iraq last month.

ISIS militants surged toward Irbil Thursday, sending thousands of Christians running for their lives and spurring the Obama administration to seriously consider airstrikes.

Earlier Thursday the U.S. began dropping humanitarian relief supplies to tens of thousands of members of a Kurdish religious minority known as the Yazidis. ISIS, Sunni militants considered more extreme than al Qaeda, views Shiites and other minorities such as Christians and Yazidis as infidels who must convert to Islam or die.

French officials called on the U.N. Security Council to convene an emergency meeting to consider how to counter the ISIS threat in Iraq.

Over the weekend, the militants seized the town of Sinjar, home to a major concentration of Yazidis, forcing them to retreat into the nearby foothills, where they are now trapped and at risk of starvation.