Islamic state crisis: Key quotes from Obama
US President Barack Obama has pressed his case to the American people about his plan to escalate US military action against Islamic State militants in Iraq and Syria.
IS controls large parts of Syria and Iraq and its fighters have become notorious for their brutality, but in recent weeks they have been subject to bombardment from US air strikes.
Here are the key quotes from Mr Obama's 15-minute address from the White House. He uses the term "Isil" to refer to IS.
Let's make two things clear: Isil is not "Islamic." No religion condones the killing of innocents, and the vast majority of Isil's victims have been Muslim. And Isil is certainly not a state.
Isil poses a threat to the people of Iraq and Syria, and the broader Middle East - including American citizens, personnel and facilities. If left unchecked, these terrorists could pose a growing threat beyond that region, including to the United States.
Our objective is clear: We will degrade and ultimately destroy [IS] through a comprehensive and sustained counterterrorism strategy.
I have made it clear that we will hunt down terrorists who threaten our country, wherever they are. That means I will not hesitate to take action against ISIL in Syria, as well as Iraq. This is a core principle of my presidency: if you threaten America, you will find no safe haven.
We will send an additional 475 service members to Iraq. As I have said before, these American forces will not have a combat mission - we will not get dragged into another ground war in Iraq. But they are needed to support Iraqi and Kurdish forces with training, intelligence and equipment.
This is American leadership at its best. We stand with people who fight for their own freedom, and we rally other nations on behalf of our common security and common humanity.
I have the authority to address the threat from Isil, but I believe we are strongest as a nation when the president and Congress work together. So I welcome congressional support for this effort in order to show the world that Americans are united in confronting this danger.
It will take time to eradicate a cancer like Isil. And any time we take military action, there are risks involved - especially to the servicemen and women who carry out these missions. But I want the American people to understand how this effort will be different from the wars in Iraq and Afghanistan. It will not involve American combat troops fighting on foreign soil.
This counter-terrorism campaign will be waged through a steady, relentless effort to take out Isil wherever they exist, using our air power and our support for partner forces on the ground. This strategy of taking out terrorists who threaten us, while supporting partners on the front lines, is one that we have successfully pursued in Yemen and Somalia for years.
When we helped prevent the massacre of civilians trapped on a distant mountain, here's what one of them said: "We owe our American friends our lives. Our children will always remember that there was someone who felt our struggle and made a long journey to protect innocent people." That is the difference we make in the world.