Raqqa is the de facto capital of the extremist group's self-styled Islamic caliphate. It is also where the militants are believed to have plotted attacks on Western nations, including last year's assault on Paris.
While the city of Raqqa is smaller than Mosul, the battle to retake it is expected to be fierce.
The first step is under way to isolate the Islamic State group's de facto Syrian capital Raqa ahead of a larger assault on the city, a USA official said Sunday. The military said Gen. Akar also voiced Ankara's disturbance over the USA -based Islamic preacher Fethullah Gülen's activities in the country during the meeting.
McGurk says that "we want this to be as coordinated as possible, recognizing that there will be a mix of forces on the field".
As the Raqqa offensive began, Turkish-sponsored groups were preparing to intervene by moving against Islamic State-held al-Bab, a strategic Syrian town 30km south of the Turkish border.
"Mosul-Raqqa can't be disassociated because Daesh and the territories it occupies span that area", he said. He said the "sophisticated surveillance effort" would give the coalition a vital edge in Syria.
The U.S.'s top soldier Gen. Joseph Dunford and Turkish Chief of General Staff Gen. Hulusi Akar discussed joint strategies against the Islamic State of Iraq and the Levant (ISIL) during the former's surprise visit to Ankara on November 6, the Turkish Armed Forces (TSK) said in a statement.
The loss of Mosul and Raqqa would deprive IS of its largest population centres, undermining the group's claim to a self-declared "state".
Last month, Defense Secretary Ashton B. Carter said a military operation targeting the city should coincide with the attack on Mosul.
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Planning for the Raqqa offensive has been complicated by factors including Turkish concerns about expanding Kurdish influence in northern Syria.
He said that as in the Iraqi city of Mosul, the target of another anti-IS offensive, "the fight will not be easy and there is hard work ahead". The Syria Democratic Forces warned civilians to stay out of the area where IS militants are present, BBC reported.
"Combined Joint Task Force-Operation Inherent Resolve Commander Lt. Gen. Stephen Townsend has said previously in Pentagon Press Corps Briefings that the Coalition supports the SDF isolation of Raqqah", it said, using an alternative spelling for the city.
Driving the militants from their urban strongholds has been the end-game since a US-led coalition launched air strikes against IS in the summer of 2014. The Observatory also said IS detonated two vehicle bombs targeting the advancing forces. The group is also known as ISIS and ISIL.
Washington's decision to support the Kurds comes despite a possible fallout with Turkey, which has been a crucial ally of the U.S. in their fight against Islamic State. Turkish officials, including President Recep Tayyip Erdogan, have said they will not accept a role for the Kurds in the liberation of Raqqa.
Both groups of Syrian fighters have been battling IS in recent months, but they have also turned their guns on each other. The tensions are exacerbated by Russian and Syrian forces on one side and Turkish forces on another. It said more than 25 children were wounded in addition to the six killed.
A coaltiion of Kurds and Arabs called the Syria Democratic Forces announced their campaign to retake the city in a news conference with troop leaders, but gave few details on how they plan to do it.
The SDF move toward al-Raqqa will surely raise the ire of Turkey, which has recently asked the United States to put the offensive on al-Raqqa on hold till the battle against IS in Mosul, Iraq subsides.
The United States would be coordinating air strikes with the SDF, which includes the powerful Kurdish YPG militia and has been the main partner on the ground in Syria for the US -led coalition against ISIS. The U.S. considers the group to be the most effective force against IS, but Turkey views it as a terrorist organization linked to a Kurdish group outlawed by the government in Ankara.