"I don't rule anything out," Obama said when asked whether the United States is considering drone strikes or any other action to stop the insurgency.
- Islamist militants vow to march on Baghdad after seizing key Iraqi Sunni cities
- Syria says it is ready to help Iraq fight jihadist 'terror'
- Al-Qaeda group takes Iraqi city
Obama, speaking to reporters at the White House as he met Australian Prime Minister Tony Abbott, said the United States has an interest in making sure jihadists do not gain a foothold in Iraq.
He said there will be short-term immediate actions that need to be done militarily in Iraq, and that his national security team is looking at all options. He said the United States is prepared to take military action when its national security interests are threatened.
Obama's former secretary of state, Hillary Clinton, said what's happening in Iraq is "a dreadful, deteriorating situation" and she's surprised by the effectiveness of the al-Qaida-inspired group that has captured major cities there.
The former US secretary of state and potential 2016 presidential contender spoke Thursday during an event at the Council on Foreign Relations in New York.
The Islamic State of Iraq and al Sham led this week's seizure of key Sunni-dominated cities in Iraq. The group has vowed to march to Baghdad.
Clinton says she was surprised by how effective the group has been at taking cities and trying to erase boundaries.
France said on Thursday world powers needed to act urgently to deal with the situation in Iraq as the advance by Islamist militants put the country's unity in doubt and posed a wider risk for the region.
"The advance of the Islamic State of Iraq and al Sham seriously puts into danger the unity and sovereignty of Iraq and ... it poses a serious threat to the stability of the region," Fabius said in a statement of ISIS fighters. "The international community must imperatively deal with the situation."
Reuters and The Associated Press contributed to this report.