"We want to confirm that Baghouz [Al-Baghouz Fawqani] is within firing range and is besieged," Syrian Democratic Forces (SDF) commander Jia Furat told reporters on Saturday.
"These days, IS is surrounded in a neighborhood estimated to be 700 meters (840 yards) long and 700 meters wide," he added.
Furat said the end of IS's self-declared caliphate in Syria would be announced in days, but the final push would be slow because the extremists were using civilians as human shields.
"In a very short time, not longer than a few days, we will officially announce the end of IS's existence," he said.
Read more: Germany arrests two Syrians suspected of crimes against humanity
Washington keen to declare victoryThe final hurdle means an announcement of an ultimate victory against the jihadis, which US President Donald Trump hoped would be made as early as Saturday, will now almost certainly be delayed.
IS, which captured large swaths of Syria and Iraq in 2014 and administered millions of people in an area the size of Britain, has been expunged by successive offensives by a US-led international military alliance.
Since late 2017, the extremist group has been confined to its heartland in the Euphrates Valley.
With the help of US airstrikes and special forces, the SDF, led by the Kurdish YPG militia, has marched into the last IS pocket near the Iraqi border.
Advancing SDF fighters have been met by "large numbers" of civilians, to the surprise of commanders who had thought the exodus of recent days had emptied the remaining IS pocket of all but die-hard fighters, an SDF spokesman said.
Residents who had endured appalling conditions were seen emerging from tunnels and foxholes beneath the battlefield.
Read more:UNICEF appeals for billions in donations for children affected by war
Humanitarian needs 'must come first'Human Rights Watch, in response, has warned SDF 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, told the AFP news agency.
The Syrian Observatory for Human Rights said around 240 IS fighters had surrendered to the advancing SDF fighters on Thursday and another 200 on Friday night.
Despite preparations to declare the final defeat of IS, Washington is facing criticism for its plan to swiftly pull its soldiers out of Syria, with some 2,000 troops expected to be pulled out within weeks rather than months, according to European diplomats.
Read more: Lindsey Graham: US must 'slow the withdrawal' from Syria to combat IS
US pullout will aid foesGerman Chancellor Angela Merkel on Saturday warned the move would allow Syrian President Bashar Assad's allies to boost their role in the region.
Speaking at the Munich Security Conference (MSC), Merkel said: "Is it a good idea for the Americans to suddenly and quickly withdraw from Syria? Or will it once more strengthen the capacity of Iran and Russia to exert their influence?"
Read more: Putin, Erdogan, Rouhani talk Syria in Sochi
US Vice President Mike Pence, meanwhile, told the MSC that Washington would continue to "hunt down the remnants of ISIS wherever and whenever they rear their ugly heads."
Despite the expected defeat on the ground, IS is believed to have sleeper cells in Syria and Iraq, which are laying the groundwork for an insurgency.
mm/ng (AFP, AP, dpa, Reuters)
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