Ten Arab nations have announced they are to join a US-led coalition against Isis (known as Islamic State) militants.
In a joint statement, Saudi Arabia, Bahrain, Egypt, Iraq, Jordan, Kuwait, Lebanon, Oman, Qatar and the United Arab Emirates, said they "will do their share" to fight against the jihadist group that has taken control of large swathes of Iraq and Syria.
The development marks a major diplomatic success for Washington and US Secretary of State John Kerry, who had embarked on a Middle East tour to lobby for a greater Arab role in the fight against extremists.
In fact, some of the ten states have tense diplomatic relations due to their rivalry on other regional issues.
Qatar and Turkey's support of the Muslim Brotherhood, for example, has put the two countries at odds with Saudi Arabia, the Emirates and Egypt.
The announcement came after Kerry met delegates from the ten countries in the Saudi government's summer seat of Jeddah.
The group of states said they assessed plans to eradicate IS "wherever it is, including in both Iraq and Syria" and pledged to join in "many aspects of a coordinated military campaign" against the militant organisation.
They also promised to support the new Iraqi government and stop the flow of funds and fighters that have boosted IS power.
Representatives from Turkey attended the meeting but did not sign the agreement and refused to let the coalition use its bases to launch air strikes in Iraq and Syria.
"Turkey will not be involved in any armed operation but will entirely concentrate on humanitarian operations," a government spokesperson speaking on condition of anonymity told AFP.
Earlier, Russia condemned Washington plan to target IS militants in Syria, saying it would consider air strikes an "act of aggression" if carried out without a UN mandate and the assent of the regime of Syria's President, Bashar al-Assad.
The US has already launched limited air strikes against IS in Iraq at the request of former Iraqi Prime Minister Nouri al-Maliki.
IS launched its offensive on Iraq from its heartland of north-eastern Syria, capturing key Sunni towns and cities such as Mosul and Tikrit. It has now declared a "caliphate" that straddles the Iraqi-Syrian border and represents a greater landmass than that of the United Kingdom.
According to the UN, over 1.6 million people have been displaced by conflict in Iraq this year while 850,000 people fled their homes in August alone.