Chelsea Manning, the former US army soldier who worked as an intelligence analyst in Iraq before being arrested for posting state secrets to WikiLeaks, says the only way to defeat ISIS is to allow the group to set up its own contained "failed 'state'" where over time, its power would "die out on its own," Gawker reported on Tuesday.

In her piece for the Guardian, Manning says her experience as an all-source analyst near Baghdad in 2009-2010 leads her to doubt the strategy being followed by the Obama administration. She warns that the US-led mission to destroy the terrorist group is destined to fail because it will merely feed a "cycle of outrage, recruitment, organizing and even more fighting that goes back decades."

Even with the support of non-western armies, attacking ISIS directly from the air or with special forces on the ground risks mission creep and the repeat of past errors. "I believe that ISIS strategically feeds off the mistakes and vulnerabilities of the very democratic western states they decry," she writes.

Presenting a radical alternative plan for how to deal with the extremist group, Manning argues that the best way to degrade ISIS is to allow it to set up a failed "state" within a clearly demarcated territory. There, ISIS would gradually become less and less popular, making them unable to govern, she predicts. The ideology of its leadership would be discredited in the region, potentially forever.

"Eventually, if they are properly contained, I believe that ISIS will not be able to sustain itself on rapid growth alone, and will begin to fracture internally. The organization will begin to disintegrate into several smaller, uncoordinated entities - ultimately failing in their objective of creating a strong state."

Manning was working at Forward Operating Base Hummer outside Baghdad as an intelligence analyst. She was arrested in May 2010 and is now serving a 35-year sentence for leaking vast quantities of secret official documents and military videos to WikiLeaks, the open-information website.