Iraqi Shiite militia fighters hold the Islamic State flag as they celebrate after breaking the siege of Amerli by Islamic State militants, September 1, 2014.
The United States plans to fight Islamic State until it is no longer a force in the Middle East and will seek justice for the killing of American journalist Steven Sotloff, President Barack Obama said on Wednesday.
He added that destroying the militant group will take time because of the power vacuum in Syria, the abundance of battle-hardened fighters that grew out of al Qaeda during the Iraq war, and the need to build coalitions, including with local Sunni communities.
Islamic State released a video on Tuesday showing the beheading of the U.S. journalist, the second American hostage to be killed within weeks, in retaliation for U.S. air strikes in Iraq.