WASHINGTON — U.S.-backed Kurdish fighters will likely not enter the Syrian city of Deir Ez-Zour. 

The fighters, known as the Syrian Democratic Forces, or SDF, have orders to clear the Khabur River Valley, but not to enter the Deir Ez-Zour, according to Col. Ryan Dillon, a spokesperson for Operation Inherent Resolve.

“The plan is to keep pressure on ISIS in the known areas where they are,” Dillon told reporters at a televised press briefing at the Pentagon.

Dillon would not provide a reason for the coalition’s reservations to SDF forces entering Deir Ez-Zour, and said that he did not want to detail the coalition’s plans for the region.

He did say the nature of the battlefield is already very “congested” and “complex,” he said. “It is already tenuous.”

On Sept. 9, SDF forces launched operations just north of the Syrian city in the Khabur River Valley. 

“The coalition supported the push into the Khabur River Valley with advisers, with equipment we have provided to elements that conducted this offensive, and we also had intelligence that was collecting throughout the area before and during the operation,” Dillon said.

SDF forces have made rapid advances in the Khabur River Valley since the start of the operation, encountering light resistance and clearing nearly 300 square kilometers of terrain, Dillon said.

“We know that to be further down the middle Euphrates River Valley, and in Mayadin, and Abu Kamal,” he said, referring to SDF and coalition plans to keep pressure on ISIS.

However, those plans have not been finalized, according to Dillon. “That is yet to be determined to be seen, and when that is going to happen,” he explained. “We are not going to tip our hat on that.”

The SDF soldiers in the operation also include local Arabs from the Deir Ez-Zour region, helping mitigate tensions that could arise from liberating the densely Sunni populations along the Euphrates River banks.

Syrian forces and Iranian proxies are present in the city battling with ISIS fighters. Just over a week ago, Syrian regime troops backed by Russian air support broke a nearly three-year siege on its forces in the embattled city.

The coalition maintains a deconfliction zone with Russian and Syrian forces that runs just south of Tabqa city and runs parallel with the Euphrates, Dillon explained. That zone continues to hold, he said. 

The U.S. decision to prohibit SDF operations inside the Syrian city may be a sign that the coalition has ceded territory to the Syrian regime, according to Jennifer Cafarella, a senior analyst at the Institute for the Study of War.

“The urban battles are the most difficult and the complexity of fighting that fight with the regime, Iranians, and probably Russians present within the city itself is too challenging for the coalition,” she said.