Pledging to "degrade and destroy" Islamic State fighters wherever they may be, president of the United States Barack Obama said he "would not hesitate" to carry out US military action against them in Syria.

"We will degrade, and ultimately destroy, ISIL through a comprehensive and sustained counterterrorism strategy," Obama said in a televised address aired Wednesday night.

"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," he added, stressing that there would be no US troops on the ground.

"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.  We’ll also support Iraq’s efforts to stand up National Guard Units to help Sunni communities secure their own freedom from ISIL’s control."

Calling on Congress to support the effort, Obama ruled out collaboration with the Assad regime and pledged further humanitarian aid for civilians affected by the violence.

"In the fight against ISIL, we cannot rely on an Assad regime that terrorizes its own people -- a regime that will never regain the legitimacy it has lost.  Instead, we must strengthen the opposition as the best counterweight to extremists like ISIL, while pursuing the political solution necessary to solve Syria’s crisis once and for all."

See full address here.

Saudi Arabia joins US coalition against Islamic State

Saudi Arabia has agreed to join the American coalition against IS fighters, by providing training for some Syrian opposition forces.

“We now have the commitment from the Kingdom of Saudi Arabia to be a full partner in this effort — the train-and-equip program — to host that program,” the NYT quoted a senior official within the Obama administration as saying.

The US Secretary of State John Kerry is currently on a tour of the Middle East, raising support for the anti-IS coalition. He was on a mission “to assemble the broadest possible coalition for this fight," he said Wednesday whilst in Baghdad, meeting with members of the Iraqi government.

Kerry is understood to meet with officials from Egypt, Turkey, Jordan, Bahrain, UAE, Kuwait, Oman and Qatar.

Syrian opposition leaders killed in blast

Obama's statement came after leaders of the Syrian opposition were killed in a blast on Wednesday, in what is widely considered to be a boost to the Islamic State.

Almost 50 leaders of the Ahrar al-Sham group, which had fought against IS forces, were killed in a blast in northwest Syria.

"It was widely seen as a bridge between moderate and more radical elements of the non-IS opposition," commented The Times.