Lasting ISIS defeat unlikely anytime soon - report

The threat from the Islamic State group will likely endure for years to come, even if it loses all the territory it once held under its so-called "

In a report, 20 experts on the Middle East and jihadism also described how organizations such as Al-Qaeda and the group formerly known as the Al-Nusra Front are adapting methods and continuing to expand.

A US-led coalition has since 2014 been striking IS targets in Iraq and Syria, pushing the extremist group out of vast areas and forcing it try to cling to two remaining power centers, Mosul in Iraq and Raqa in Syria.

Coordinated by the United States Institute of Peace (USIP), the report highlights how the relatively narrow military focus overlooks broader issues that enabled the rise of groups like IS.

"Eliminating an extremist group physically does not defang its ideology or change the underlying circumstances that allowed the group to gain traction in the first place," the report states.

"Reconstruction, rehabilitation and particularly reconciliation are just as important as any military counterterrorism campaign in building societal resilience against the appeal of extremism. Failure to carry out these steps has been a recurrent problem."

The report highlights regional youth unemployment, with the rate of jobless youths in Gaza and the West Bank now 43 percent, 35 percent in Iraq, and 42 percent in Egypt.

As the coalition chips away at IS, the group retains appeal for would-be jihadists, the report notes, saying IS will likely endure for "years to come as a pure insurgency using terrorist tactics."

"It revolutionized mobilization of supporters and sympathizers in the West, a lasting legacy as well as a future threat," it adds.

Meanwhile, another extremist group has grown rapidly in Syria.

Fateh al-Sham, the former Al-Qaeda affiliate previously known as Al-Nusra Front, now has about 10,000 fighters, with nearly a third of its ranks coming from Russia, Europe and elsewhere in the Middle East, the report states.

Additionally, Al-Qaeda has persisted despite the 2011 death of its leader Osama bin Laden.

The report describes how the organization has become an increasingly savvy political operator, while IS relies on ruthlessness and brutal coercion to hold power.

Al-Qaeda "has demonstrated an ability to evolve and adapt to shifting political trends," the report states.

"In the future, Al-Qaeda has the potential to be a greater jihadist threat than" IS, it says.

President-elect Donald Trump has claimed he would "bomb the shit" out of the IS group, though he offered few details.

Such rhetoric is unlikely to help matters, the report notes.

"The jihadist agenda is likely to be heavily defined by where and how -- and how much -- the outside world intrudes. The larger the intervention, especially by the West, the greater the reaction," it states.