FILE - A still image, taken from video footage and released by Russia's Defence Ministry on Aug. 18, 2016, shows a Russian Sukhoi Su-34 fighter-bomber based at Iran's Hamadan air base, dropping bombs in the Syrian province of Deir Ezzor.
FILE - A still image, taken from video footage and released by Russia's Defence Ministry on Aug. 18, 2016, shows a Russian Sukhoi Su-34 fighter-bomber based at Iran's Hamadan air base, dropping bombs in the Syrian province of Deir Ezzor.

As the Syrian government forces, backed by allied militias and Russian airstrikes, continue to advance against the Islamic State group in Deir el-Zour, Syria, the U.S.-led coalition says it is monitoring the army to ensure it does not cross a deconfliction zone established across the city.

"We do monitor and watch where they are and where they are going at the same time as they move closer to the middle of the Euphrates Valley," Colonel Ryan Dillon, spokesman for the U.S.-led coalition against IS, told VOA on Thursday.

Dillon added that the coalition warplanes were continuing to strike IS positions in Deir el-Zour as the U.S-backed Syrian Democratic Forces (SDF) partnered with local tribal militias in preparation for an attack from the northeast of the deconfliction line.

He did not disclose a timeline for the assault.

The deconfliction zone in Deir el-Zour was established between the U.S. and Russia in late 2015 to separate their areas of operation in Syria and prevent inadvertent clashes between the two sides.

The vast line starts from the town of Tabqa, roughly 45 kilometers west of IS's self-proclaimed capital, Raqqa, and extends parallel to the Euphrates River that runs across Deir el-Zour toward Al-Bukamal town bordering Iraq. It has divided Deir el-Zour province and city into two parts; SDF operates north and east of the line, and the Syrian government troops and their allied militias are in the west and south.

"We will continue to deconflict as necessary and as required," Dillon said while speaking to reporters in Washington during a teleconference briefing from Baghdad. "We will continue to draw that line … farther and down the Middle Euphrates River Valley."

Deir Ezzor Syria
Deir ez-Zor, Syria

Earlier this week, the Syrian army and its allied Shi'ite militias, backed by heavy Russian airstrikes, made significant gains against IS in the western parts of Deir el-Zour. Syrian regime forces were able to enter the outskirts of the city and break a three-year IS siege of an enclave known as Regiment 137.

IS still controls pockets

IS still controls much of the city and the wider oil-rich province that stretches to the Iraqi border. An estimated 2,500 IS fighters are thought to be in the province to defend their positions in one of the terror group's last major strongholds in Syria.

Rabee Hamidi, a spokesman for Jaish Maghawir al-Thawra (MaT), a rebel group consisting of local Deir el-Zour fighters supported by the U.S.-led coalition, told VOA that Syrian regime forces had established control over some isolated areas on the western outskirts of the city.

He said the regime's progress would most likely be stalled as government forces approached more densely populated neighborhoods.

"IS is launching counterattacks by sending suicide bombers. The area is under fierce air raids," Hamidi told VOA.

He added that MaT and other U.S.-backed forces were prepared to attack from the town of al-Shaddadi, about 85 kilometers northeast of Deir el-Zour, but warned that safety corridors to allow civilians to flee from the city needed to be opened in advance to keep them from getting caught in the crossfire.

A woman who had just fled Deir el-Zour talks on a
A woman who had just fled Deir ez-Zor talks on a mobile phone beside a truck with her belongings at a camp in Ain Issa, north of Raqqa, Syria, Aug. 12, 2017.

A million civilians    

More than a million people are estimated to live under IS-controlled areas in Deir el-Zour. Observers expect a complicated battle as IS, the U.S.-backed forces and the Syrian regime, backed by Russian air support and Iranian-allied Shi'ite militias, compete for the strategic province, and U.N. officials have expressed concerns about civilian casualties.

"The fight in the city will be long and difficult. We should not expect a rapid victory for the Syrian army in Deir el-Zour," Robert S. Ford, a former U.S. ambassador to Syria, told VOA.

He said the Syrian regime's recent advances in the province had most likely taken Washington by surprise.

"This complicates the American decision, because if they go there, would they fight with [Syrian government] forces against ISIS?"

Ford added that a race for the province and its natural resources was imminent and inevitable.

"Deir el-Zour is for whoever captures the middle of the city," he said.