U.S. military officials have not yet determined which faction of local ground forces will launch the offensive.
Whether or not Raqqa is taken by Kurdish or Syrian Arab forces could determine whether U.S. troops are needed afterward in the city.
A small number of U.S. troops is currently in the Syrian town of Manbij to keep the peace between the Kurdish and Turkish forces. Turkey invaded Syria in large part to prevent the Kurds from linking up their two autonomous enclaves inside Syria.
The deployment of Marines is temporary, so they will leave Syria as soon as their support is no longer needed, the official said. News of the Marines arriving in Syria was first reported Wednesday by the Washington Post.
This marks the second time in as many years that Marines have provided artillery support for allied forces fighting ISIS. In March 2016, about 180 Marines from the 26th Marine Expeditionary Unit spent about 60 days at the Kara Soar Counter Fire Complex in Makhmour, Iraq, near Mosul.
Known as Task Force Spartan, the Marines used four 155 mm M777A2 howitzers to fire more than 2,000 rounds in support of Kurdish and Iraqi troops. The firebase was 15 miles from ISIS forces, which often fired rockets at the Marines, Col. Robert Fulford, commander of the 26th Marine Expeditionary Unit, said last year.
On March 19, 2016, one ISIS rocket attack killed Marine Staff Sgt. Louis Cardinand wounded eight other Marines.
Task Force Spartan returned to Camp Lejeune, North Carolina, on June 3. They were replaced by about 200 soldiers with the 1st Battalion, 320th Field Artillery Regiment from the 101st Airborne Division (Air Assault).
The Associated Press and Military Times reporter Shawn Snow contributed to this story.