The head of the SDF media office, Mustafa Bali, told Reuters that the main battle will be launched on the evening of February 9 and its mission will be to eliminate the last remnants of "the terrorist organization".
The final territory controlled by fighters of the so-called Islamic State was in the small town of Baghouz Al-Fawqani, just west of an earthen berm on the outskirts of the village where US-backed Syrian Democratic Forces started their push.
As Kurdish forces prepare to advance o the ISIS-held enclave, more than 20,000 civilians have been evacuated, an SDF official said.
The besieged ISIS enclave centred around Baghouz on the eastern bank of the Euphrates River represents the terrorist group's last territorial foothold in the part of Syria where forces supported by the United States have been fighting it.
Maj. Gen. Christopher Ghika, the coalition's deputy commander, described the size of the last IS pocket as "now less than 1 percent of the original caliphate".
In recent days, President Trump has said the total defeat of IS could be declared next week.
Kurdish authorities say they have in their custody hundreds of foreign male IS members.
Thousands of suspected IS fighters have attempted to blend in with civilians fleeing the jihadist group's battered last bastion, including a large number of foreigners.
Storm Erik to hit Limerick as Met Eireann issues nationwide wind warning
A yellow weather warning is in place for the rest of Ireland but will last only an hour, expiring at 6am on Friday. Wet weather will follow later as rain moves in across the United Kingdom , and some of it could be heavy at times.
The SDF said it has not been in communication or agreed the ceasefire with IS.
On Thursday, the coalition said the "caliphate" had massively shrunk.
More than 37,000 people, mostly wives and children of jihadist fighters, have fled ISIS territory since the SDF, backed by the US-led coalition, intensified its offensive in December, according to the Observatory.
An SDF statement said the offensive was focused on the village of Baghuz. "Those remaining inside are the most experienced who are defending their last stronghold".
The Kurdish People's Protection Units (YPG) and their female equivalent, the Women's Protection Units (YPJ), have formed the backbone of the SDF.
Among the policy decisions still to be made was what to do about the tens of thousands of Syrian Kurdish fighters that U.S. forces had trained, armed and advised to carry out the ground war against the Islamic State.
This suits his agenda of withdrawing all USA troops from Syria.