Kurdish-led Syrian forces, backed by U.S. air power and military advisers, launched an offensive Sunday to gain control of Raqqa, the northern Syrian city overrun by Islamic State extremists in 2014 and self-designated as the center of extremist rule.
A commander of the Syrian Democratic Forces (SDF) announced the start of the campaign Sunday.
The U.S. envoy in charge of anti-IS efforts confirmed the SDF, a Kurdish-led group that also includes Arab fighters, is receiving American air support in the operation.
"The Raqqa campaign will proceed in phases," Brett McGurk said from the U.S. embassy in Amman. "There’s an isolation phase, which began today, and there will be subsequent phases to make sure that we kick Daesh (IS) out of Raqqa," he added, using an alternate name for the armed extremist group.
McGurk also said the chairman of the U.S. Joint Chiefs of Staff, Gen. Joseph Dunford, met in the Turkish capital Sunday with his Turkish counterparts, including Gen. Hulusi Akar, chief of the Turkish general staff, for talks on the new offensive.
WATCH: McGurk on Raqqa operation
Those talks appear aimed at easing Turkish concerns about the makeup and objectives of the SDF, which Washington considers the most potent anti-IS fighting coalition in territory near the Turkish border.
For its part, the Ankara government views the main SDF component -- the Syrian Kurdish fighting force known as the People's Protection Units -- as a terrorist organization with links to yet another Kurdish force fighting government forces in southeast Turkey for regional autonomy.
Turkish officials went so far last week as to suggest that Turkish-backed forces take the lead in the push to free Raqqa rather than the Kurdish-led SDF.
Watch video report from VOA's Zlatica Hoke:
A Pentagon statement late Sunday said the two generals agreed to "consult closely" on the coalition plan to seize and hold Raqqa, and to work collaboratively to disrupt IS operations in Syria and in Iraq.
The Raqqa offensive comes as a separate coalition of Iraqi-led forces some 450 kilometers to the east battles to recapture the northern Iraqi city of Mosul from IS control.
U.S. Defense Secretary Ash Carter, speaking Sunday, said the international coalition will continue to do what [it] can to enable local forces in both Iraq and Syria to deliver [Islamic State] the lasting defeat it deserves."