Even as U.S.-backed forces close in on the very last pockets of the Islamic State's self-declared caliphate in Syria, the terror group is unfazed, instead preparing to declare victory and retake territory.

The sobering assessment by U.S. Central Command and relayed to the lead inspector general for U.S. efforts in Iraq and Syria comes just over a month after U.S. President Donald Trump announced plans to withdraw some 2,000 U.S. troops from Syria, declaring the fight against IS over.

But far from agreeing with the president’s assessment that the United States has “beaten them and we’ve beaten them badly," U.S. military officials warned the terror group is poised for a resurgence, should U.S. forces actually leave Syria.

“Absent sustained [counterterrorism] pressure, ISIS could likely resurge in Syria within six to 12 months and regain limited territory,” U.S. Central Command told the inspector general, using an acronym for the terror group, in the report released Monday.

"ISIS may conduct opportunistic attacks on U.S. personnel as they withdraw but will leverage the event as a 'victory' in its media," Central Command added, further warning the terror group is "regenerating key functions and capabilities" both in Syria and in Iraq.

The U.S. military commanders also said the inability of Syrian and Iraqi officials to address long-standing Sunni Arab grievances could make IS even more potent.

"It is very likely that ISIS will have the opportunity to set conditions for future resurgence and territorial control," they said.

This latest U.S. military assessment of the strength of IS forces in Syria and Iraq follows similar reports over the past six months warning about the terror group's resiliency and long-term planning.

As far back as August of last year, U.S. military intelligence officials cautioned that IS still had a fighting force of 13,000 to 14,500 fighters in Syria, with as many as another 17,000 in Iraq.

In response, Pentagon officials said the group was "well-positioned to rebuild and work on enabling its physical caliphate to re-emerge."

In December, just days before Trump announced his plans to pull U.S. troops from Syria, then-special presidential envoy Brett McGurk warned despite key advances against IS in Syria, "it would be reckless if we were just to say, well, the physical caliphate is defeated, so we can just leave."

Yet despite losing even more ground in the weeks since then, U.S. military officials caution IS remains, "a battle-hardened and well-disciplined force ... able to coordinate offensives and counter-offensives."

Officials with Operation Inherent Resolve, the U.S. mission in Iraq and Syria, also caution that morale among IS fighters, while not as high as it once was, remains high overall.

At times, IS fighters even appear to be "unfazed by coalition airstrikes," the officials told the inspector general. (VOA)

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