Assaults would aim to drive the jihadist militants out of areas they hold north and east of the Euphrates river, close to the Iraqi border, said the statement from the Deir Al-Zor Military Council, which is fighting as part of the Syrian Democratic Forces alliance (SDF).
A senior SDF official told Reuters on Friday they would launch attacks from the south of Hasaka, which is controlled by the Kurdish YPG militia, as part of a wider offensive to drive Daesh out of Raqqa city and territory to its southeast.
With US-led air cover and special forces on the ground, the alliance of mostly Kurdish and Arab militias is fighting to seize Raqqa, upstream along the Euphrates River.
Spearheaded by the YPG, the SDF says it has taken 65 percent of Raqqa city from Daesh.
In the Deir Al-Zor assault, the SDF would push toward the Euphrates River from the east of the province, which borders Iraq.
The Syrian Observatory for Human Rights monitoring group reported that the SDF had already made advances against Daesh in Deir Al-Zor after fierce clashes and seized several hills and a village in the province’s northwestern countryside.
The operation will likely bring the US-backed militias into closer proximity with the Syrian military and allied forces, who have advanced on Deir Al-Zor city.
The Syrian army reached its enclave in Deir Al-Zor city this week, on the western bank of the Euphrates, breaching an Daesh siege that had lasted three years.
With the help of Russian air power and Iran-backed militias, the advance capped months of steady progress east against Daesh across the desert.
The eastwards march has on occasion brought the Syrian army and its allies into conflict with US-backed forces.
Still, the rival campaigns have mostly stayed out of each other’s way, and the US-led coalition has stressed it is not seeking war with Damascus.