Militant fighters defending the last dreg of the once vast ISIS territory on Saturday were holed up in half a square kilometre in a village of eastern Syria but the appearance of hundreds of civilians has slowed the final push.
US President Donald Trump said the fall of the ISIS proto-state would be announced on Saturday.
The capture of the last pocket of ISIS fighters in the village of Baghouz would mark the end of a devastating four-year global campaign to end the extremist group's hold on territory in Syria and Iraq.
"ISIS is besieged in a neighbourhood that is estimated to be 700 metres long and 700 metres wide" in the village of Baghouz, said Syrian Democratic Forces (SDF) commander Jia Furat.
He said that SDF fighters were able to liberate 10 of the fighters that were held by ISIS.
But a top Syrian commander said his forces had slowed down their advance to protect civilians.
Thousands of people have flooded out of eastern Syria’s Baghouz over the past week – mostly women and children related to ISIS fighters, but also suspected militants themselves.
But an SDF spokesman said there were "still civilians inside in large numbers".
"We weren't expecting this number, otherwise we wouldn't have resumed the campaign four days ago. This is why it's been delayed," SDF spokesman Adnan Afrin said.
SDF spokesman Mustafa Bali said "we are dealing with this small pocket with patience and caution. It is militarily fallen but civilians are used as human shields." Bali added that the SDF believes that ISIS gunmen are also holding previously kidnapped Syrians in the area.
A spokesman for the US-led coalition, Col Sean Ryan, acknowledged that the timeline had slipped because of the presence of civilians inside.
"There have been lapses as we continue to see hundreds of civilians still attempting to flee to safety," he said.
"The area of Baghouz has many tunnels, which slows operations," he added.
Human Rights Watch called on commanders not to try to accelerate the offensive to suit Trump's timetable.
"The tempo of battle must not be dictated by political imperatives – it must, first of all, protect civilians and possible hostages," HRW's Director of Counterterrorism Nadim Houry said.
The Syrian Observatory for Human Rights said ISIS fighters were surrendering in large numbers to the advancing SDF fighters.
The British based war monitor said that some 200 ISIS gunmen had surrendered on Friday, days after about 240 others surrendered and were taken by SDF fighters and members of the US-led coalition.
Men are being split from women and children and taken to displacement camps several hours drive from the front lines.
Meanwhile, in the UK a national debate rages over what to do with British nationals who travelled to Syria and Iraq to join ISIS. The question has been prompted by news that pregnant London schoolgirl, Shamima Begum, wishes to return home. She ran away with two friends, flew on their own to Turkey and crossed into Syria in 2015.
The Telegraph newspaper has now reported that a mother and her two daughters from Manchester are also in Kurdish displacement camps in Syria having fled the frontlines.
Safiya Zaynab, 51, Shabina Aslam, 29 and Alireza Sabar, 17, are from the town of Didsbury.
Unlike the unrepentant Ms Begum who spoke to The Times newspaper, Shabina Aslam expressed confusion and claimed that she had ended up with the militant group after a relative took them on holiday to Turkey but they ended up in Syria. She said they have been trying to escape since then but were unable to.
“I don’t regret anything because we came on a holiday which then turned into this,” she told the paper. “It has never been explained to me."