PENTAGON - A top U.S. military official is pushing back against the Pentagon's own estimates which suggest the Islamic State terror group has retained significant capabilities in Iraq and Syria, and is "well-positioned" to rebuild its lost caliphate.
Chairman of the Joint Chiefs of Staff, Marine Gen. Joseph Dunford, challenged recent estimates from both the U.S. Defense Department and a United Nations report, indicating IS still has anywhere from 20,000 to 32,000 fighters in the two countries despite the collapse of its self-declared caliphate.
"I saw the recent reports of over 30,000 fighters," Dunford told reporters Tuesday during a rare news conference with Defense Secretary James Mattis at the Pentagon. "I don't have high confidence in those particular numbers.
"We're focused on dealing with what remains a threat in [the] Euphrates River Valley. We know there are remaining residual pockets of ISIS inside Iraq," Dunford added, using an acronym for the terror group. "But I certainly would not say ISIS has the same strength that it had at its peak."
WATCH: Dunford Discusses IS Numbers
?Defense and intelligence officials have long been wary of using numbers alone to measure the effectiveness of the campaign to destroy IS, calling any such effort, at best, an imperfect science. And some senior officials have likewise voiced concerns, internally, that the newest estimates may be misleading, possibly counting family members or others with strong connections to IS, though not themselves likely to fight.
Iraq, Syria IS force strength
But the new estimates, contained in a report issued by the lead inspector general for Operation Inherent Resolve, along with a subsequent report from the United Nations, have raised concerns.
The inspector general report, citing Defense Department figures, said IS likely had more than 17,000 fighters in Iraq and another 13,100 to 14,500 in Syria, only 4,000 to 6,000 "remained in the U.S. military's areas of operation."
Together, the numbers come close to the U.S. Defense Department estimates of the size of the IS fighting force at its peak in 2015, when officials said the group had about 33,000 fighters at its disposal.
When questioned about the new estimates, the Pentagon told VOA via an emailed statement that IS "is well-positioned to rebuild and work on enabling its physical caliphate to re-emerge."
Such assessments are a dramatic departure from previous characterizations of the scope of the IS threat, in which collation officials have described a terror organization in "disarray" with fighters "hiding in onesies and twosies amongst the population."
The new estimates have been even more alarming given that, to date, the U.S.-led coalition has carried out about 24,000 airstrikes, killing close to 70,000 IS fighters, according to some U.S. military officials.
Still, Dunford on Tuesday downplayed the significance of any estimates regarding the number of IS fighters.
"Here's what I'm confident of — that over the last two-and-half years, ISIS has lost about 98 percent of the ground that they've held," he said. "They've lost significant access to resources and the flow of foreign fighters has been significantly reduced. Those are all quantifiable."
'Fight is not over'
Dunford said, for now, the U.S. focus is on clearing out the last remaining "significant" pocket of IS fighters, cornered in a small area of Syria's Middle Euphrates River Valley, an operation slated to get under way shortly with the help of the U.S.-backed Syrian Democratic Forces.
WATCH: Syrian civil war
?Once that is done, the challenge will be to stabilize the area so that IS cannot return, which Dunford said, "is going to take some time to do."
"We recognize the fight is not over," Defense Secretary Mattis said, standing alongside Dunford, adding the approximately 2,000 U.S. troops stationed in Syria will stay there until ISIS is "taken out."
"If the locals are able to keep the security, obviously during this time we might be reducing our troops commensurate with their ability to deny ISIS a return," he said.
Yet aside from numbers of fighters, there are other indications the terror group is far from destroyed.
Just last week, IS's reclusive leader, Abu Bakr al-Baghdadi, broke his silence for the first time in almost a year, urging his followers to be patient.
"For the mujahedeen, the scale of victory or defeat is not dependent on a city or town being stolen or subject to that who has aerial superiority, intercontinental missiles or smart bombs," Baghdadi said in a recording released on social media.
There have also been more reports of a resurgent IS force in Iraq, with attacks reported in recent weeks in Diyala, Salah ad-Din and Kirkuk.
"It would be a mistake to think that the threat has dissipated and that this is just a mop-up operation at this point," Daveed Gartenstein-Ross, a senior analyst at the Washington-based Foundation for Defense of Democracies, told VOA.
Gartenstein-Ross has long thought the initial U.S. estimates for IS fighters in 2014 and 2015 were far too low, arguing the terror group likely had close to about 100,000 fighters at its peak.
But he said the newer estimates of up to about 32,000 IS fighters could well be accurate.
"They have lost territory. There's no question. They have fewer resources," he said. "The flipside is we've seen this before. Groups like ISIS, after they reach a point where they can no longer control territory, try to come back as insurgent forces, and that's where numbers matter."
Carla Babb contributed to this report at the Pentagon.