The Islamic State (ISIS) is losing territory and power and that the United States would need just three months to completely defeat its forces in Iraq and Syria with "the right mix of troops and air power."

The assessments came from two U.S. officials speaking on separate occasions on Sunday.

Brett McGurk, U.S. presidential envoy to the 66-nation anti-ISIS coalition, said the tide of battle has turned against the jihadist-terrorist group, CBN News reports.

"This perverse caliphate is shrinking," he said, adding that aside from losing territory, ISIS is also losing the war over online social media propaganda.

McGurk said the U.S. has intensified its offensive against the ISIS use of social media to radicalise and recruit jihadists amid a round-the-clock counter-propaganda campaign involving companies like Facebook and YouTube as well as the Jordanian government, Malaysia, and the United Arab Emirates.

"For every pro-Daesh Twitter handle, there are now six calling out its lies and countering its message," McGurk said.

The loss of territory and power is the reason why ISIS is now only able to launch small coordinated attacks.

But these insurgency-style strikes have killed more than 100 people this past week, reports say.

Just this weekend, the ISIS launched a deadly suicide bombing against a natural gas plant north of Baghdad that left at least 14 people dead.

Meanwhile, retired Army Maj. Gen. Paul E. Vallely said the terror group could be eliminated in just 90 days.

Interviewed on Newsmax TV, the senior Fox News military analyst bared parts of the strategy to finally put an end to the widely despised group.

"We could defeat ISIS in 90 days with the right mix of troops and air power and ground operations, along with the Kurds and the Free Syrian Army. It can be done. I know that having been on the ground over there, Vallely said.

He said the U.S. need not throw in thousands of soldiers to do the job since it will only involve "Joint Strike Force raids, use of Special Operations forces, good intelligence, and good targeting."

He likened his envisioned campaign to what the U.S. did against the Taliban and al-Qaeda in Afghanistan in late 2001, when the U.S. military just used 100 men and air power to defeat those forces in 31 days.

"So this can be done, but you have to have the right minds, the right strategy and tactics and right positioning of our forces to do that and it can be done in a short period of time. Don't let anybody tell you differently," Vallely said.