Yesterday the Islamic State (IS), formerly known as ISIS, stormed the country's biggest Christian town.
Thousands of people had to flee Qaraqosh in the middle of the night to escape the jihadists.
The President said American troops would not be sent back to Iraq and any involvement would be to protect American interests.
US aircrafts have already made humanitarian air drops to provide support for religious minorities stuck up a mountain.
IS fighters surrounded members of the Yazidi community who were trapped on Mount Sinjar.
The UK government says it will take no part in military action.
Mr Obama said: "Today I authorized two operations in Iraq — targeted airstrikes to protect our American personnel, and a humanitarian effort to help save thousands of Iraqi civilians who are trapped on a mountain without food and water and facing almost certain death.
"I said in June — as the terrorist group ISIL began an advance across Iraq — that the United States would be prepared to take targeted military action in Iraq if and when we determined that the situation required it. In recent days, these terrorists have continued to move across Iraq, and have neared the city of Erbil, where American diplomats and civilians serve at our consulate and American military personnel advise Iraqi forces.
"To stop the advance on Erbil, I've directed our military to take targeted strikes against ISIL terrorist convoys should they move toward the city.
"As ISIL has marched across Iraq, it has waged a ruthless campaign against innocent Iraqis. And these terrorists have been especially barbaric towards religious minorities, including Christian and Yezidis, a small and ancient religious sect. Countless Iraqis have been displaced. And chilling reports describe ISIL militants rounding up families, conducting mass executions, and enslaving Yezidi women.
"As Commander-in-Chief, I will not allow the United States to be dragged into fighting another war in Iraq. And so even as we support Iraqis as they take the fight to these terrorists, American combat troops will not be returning to fight in Iraq, because there's no American military solution to the larger crisis in Iraq."
Meanwhile the Archbishop of Canterbury Justin Welby has tweeted about the situation:
Church meetings Manila dominated by events in Iraq, Israel/Palestine, Syria and forgotten wars, Nigeria, S Sudan, CAR & more. #prayforpeace.