"We are working very closely with our partnered force to further isolate Raqqa. There is still plenty of ISIS [Daesh] fighters, and still plenty of ISIS leaders in Raqqa," Dorrian told reporters.
"In these other areas, like Deir ez-Zor, that may be where we go next."
Last Friday, the US State Department disclosed its intention to carry out an operation to liberate the Syrian Raqqa from Daesh terrorists together with Turkey and coalition partners.
At present, Daesh controls vast territories of Syria's Raqqa province, including the regional capital itself.
The Syrian government-held city of Deir Ez-Zor has been under siege from Daesh since July 2014.