Britain is at greater risk of a Paris-style terror attack as so-called Islamic State (IS) loses ground in Syria and Iraq, a top coalition spokesman has warned.
IS, also known as Daesh, are "beginning to crack" under the pressure of Western-backed air strikes and attacks on their recruitment and finances.
But as they are being "squeezed" in their so-called caliphate, they are more likely to lash out and carry out atrocities in the West to assert themselves, Colonel Steve Warren, spokesman for the anti-IS coalition, said.
He said: "As we squeeze them and we begin to see them get chipped away at inside Iraq and Syria, we are going to see them look for other avenues.
"We have seen this in Libya, we have seen it in parts of North Africa and Afghanistan, we have seen this through high visibility terror attacks in places like Paris, possibly San Bernardino, Ankara, other places.
"What I do know is that we have assessed that as we continue to squeeze this enemy, as this enemy continues to feel that it's back on its heels, our assessment is that one of the responses to that - it really is in desperation, that they are going to want to show the world that they are still viable - and one of the ways they can do that is through a high visibility attack outside of their so-called caliphate borders."
He said an attack like the one in Paris, when 130 people were killed in co-ordinated strikes across the city, is not a sign of strength.
"We view it exactly the opposite", he said.
"We view it as a sign that because of the pressure that has been placed on them, because they are beginning to stumble a little bit, they are trying to either distract or prove that they are not finished yet."
Speaking to British journalists at the Foreign Office in London, Baghdad-based Col Warren painted a picture of an increasingly desperate IS.
He said the terror group is floundering under the onslaught of air strikes and counter-terror measures, while the flow of foreign fighters into Iraq and Syria is decreasing as would-be jihadis realise "this caliphate isn't all unicorns and rainbows".
The group has slashed wages for its fighters, and is resorting to increasingly desperate measures including recruiting child soldiers and hiding bombs in copies of the Koran to keep hold of its territory, he said.
Speaking on a trip to Britain, he said: "We believe that Daesh is now beginning to lose. We see them in a defensive crouch."
He added: "We are beginning to see the fraying around the edges of this outfit as they begin to crack underneath this pressure."
IS has suffered a series of setbacks in recent months and has lost territory to Iraqi security forces.
Col Warren said the extremists have resorted to horrific and desperate measures to cling on to power, including booby trapping areas they have been forced out of.
He said: "These guys are disgusting, they have left bombs in refrigerators, they have put bombs in toilets, they have put bombs inside the holy Koran - we found that on several occasions in Ramadi."
As the tide of foreign fighters streaming into the country has stemmed, IS has resorted to forcing children to take up arms, he warned.
He said: "We have seen an increase in enforced conscription. We have seen an increase in the number of child soldiers, which is particularly concerning."
Elite forces are also being "farmed out to the grunt units" to beef them up, he added.
Col Warren warned that any British jihadis thinking about travelling to Iraq or Syria will probably be killed - either by air strikes or by IS itself.
He claimed that message is beginning to get out, with a reduction of foreign fighters pouring into the region.
He said: "I would like to attribute that to success - success of our efforts to show that the caliphate is not all the unicorns and rainbows that Daesh wants people to think it is.
"That word is starting to get out a little bit. If you move to the caliphate you are probably going to get killed by somebody."
But he warned the coalition is "not going to kill our way out" of the crisis, and peace will only be achieved through diplomacy.
Shashank Joshi, a senior research fellow at the Royal United Services Institute (RUSI) security think-tank, said "the picture is more balanced than the coalition is saying".
He said that while forces made several important gains, such as the retaking of the Iraqi city of Ramadi, they have done this by "plucking the low-hanging fruit" - but it will take years to defeat IS, also known as Isis.
He told the Press Association: "We are containing them very well, we are stopping them grow, the threat is far less than it was two years ago when we were worried that places like Baghdad might fall.
"On the down side I would say what we have been doing is plucking the low-hanging fruit. So it is one thing to contain Isis and one thing to expel them from the city of Kobani in northern Syria, but this is not the same scale of challenge as retaking a major city like Mosul.
"That kind of serious, intense urban warfare is ultimately going to be the challenge we face in expelling Isis from Iraq and Syria."
He said it will take several years to defeat IS in Iraq and Syria, and warned the coalition could be facing a "whack-a-mole" problem as jihadi fighters wage war in other parts of the Arab world such as Libya and Egypt.
He said: "This coalition is not a coalition about Iraq and Syria, it is a coalition against Isis. And Isis is not just a force in Iraq and Syria, it has thousands and thousands of personnel in Libya and in Sinai in Egypt, it has forces in Pakistan and Afghanistan.
"You are facing a situation where even if you can weaken Isis in the core of their territory, you have a serious Isis problem that goes well beyond Syria and Iraq.
"That's going to mean a sort of whack-a-mole problem develops whereby you can roll Isis back in the middle, but what if you have a new Isis problem somewhere else?"