BEIRUT - The fight to wrest a desert area in eastern Syria from the Islamic State group will take "much longer than expected", US-backed forces battling the jihadists said on Tuesday.
The reassessment came as the United Nations warned that the fight for Hajin in Syria's eastern province of Deir Ezzor was having a "devastating" effect on thousands of civilians.
The Syrian Democratic Forces has been locked in clashes for just over a month with IS holdouts in Hajin and surrounding villages, but they have been slowed down by harsh weather conditions and a ferocious jihadist fightback
"The military operations in Hajin will take much longer than expected," said Redur Khalil, a top SDF commander.
"Daesh is benefiting a lot from weather factors, including sandstorms. They've helped it take cover from reconnaissance aircraft and other monitoring mechanisms," he said, using an Arabic acronym for IS.
Khalil said the landscape around Hajin was vast and arid, "larger than just a pocket".
The SDF estimates some 3,000 jihadists are defending the area.
They have laid a massive network of trenches, barriers, and explosives that were "hindering" the SDF's advance, Khalil said.
"Most of the fighters in the Hajin region are foreigners with fighting experience," he added.
Hajin, which lies in a small stretch east of the winding Euphrates River, is one of IS's final holdouts in Syria.
The jihadist group lost its de facto Syrian capital Raqa one year ago this week to the SDF, which has chased it out of swathes of the country's north and east.
The SDF has been advancing on Hajin since September 10 but IS launched a bloody fightback last week.
The ensuing clashes have killed more than 70 SDF fighters and dozens of IS jihadists, according to the Syrian Observatory for Human Rights war monitor.
The Britain-based Observatory said IS had even raided a nearby displacement camp and took "more than 100 families", including relatives of IS defectors and of jihadists killed in fighting.
The UN on Tuesday warned the recent fighting was endangering civilians.
"The ongoing violence in the Hajin area in the eastern governorate of Deir Ezzor is having a devastating impact on civilians," the UN's office in Syria said Tuesday.
It estimated that around 7,000 people had been displaced by fighting over the past month to SDF-controlled camps, and that another 10,000 people were at risk.
Accessing civilians in need of aid was extremely difficult.
"The UN calls on all parties involved to protect civilians and to support greater access to the area as required under International Humanitarian Law," it said.