U.S. Secretary of State John Kerry heads to Turkey Friday to help build international support in the fight against Islamic State extremists.
During talks with Kerry on Thursday in Saudi Arabia, Turkey refused to endorse a U.S.-led comprehensive plan to defeat the Islamic State militants.
Ten Arab nations did join the coalition, promising to help the U.S. destroy the Islamic State wherever it is, including Iraq and Syria.
A statement said the coalition would stop the flow of foreign fighters, cut off funds for the group, and provide aid to those terrorized by it. Where appropriate, it said they would also participate in "the many aspects of a coordinated military campaign."
Turkey, which has a 900-kilometer-long border with Syria, has been reluctant to take an active role in the coalition. Islamic State fighters are currently holding 49 Turks, including diplomats and their families, who were kidnapped from a consulate in June.
U.S. intelligence authorities said Thursday the Islamic State is more powerful than they originally estimated. The Central Intelligence Agency says the group has between 20,000 and 31,500 fighters on the ground in Iraq and Syria. This is much higher than the previous estimate of 10,000.
The agency says the new estimate reflects stronger recruitment by the Islamic State since June following success on the battlefield and the declaration of a caliphate in Iraq and Syria.
President Barack Obama this week unveiled his long-term plan for degrading, and ultimately destroying the Sunni extremist group. This includes continuing U.S. airstrikes in Iraq, as well as possibly expanding the military campaign to Syria.