The elite military unit has been ordered to take down Abu Bakr al-Baghdadi in a “kill not capture mission”.
Defence chiefs in both Britain and the US believe eliminating the ISIS leader is the best chance of defeating the terror cell for good.
They hope that by cutting off the head the body will die, in a similar way to al-Qaeda, which has never fully recovered from the death of leader Abu Musab al-Zarqawi in 2006.
MI6 and GCHQ are now putting all resources into tracking down and killing al-Baghdadi.
The assassination plot will be led by top SAS snipers, while covert squads monitor hideouts in Iraq and Syria.
Spy planes will intercept emails and phone calls, with additional intelligence coming from MI6 and CIA double agents who have deserted al-Baghdadi after seeing atrocities carried outing his name.
Speaking to the Daily Star Sunday, an unnamed defence source said: “The head of IS is now a priority target. That means the SAS will be using all of their experience and skill to track him down.
“He is a dead man walking, it’s just a matter of time.
“He’s going to be killed by ground troops or taken out in an air strike or drone strike.”
Over the years there have numerous reports of al-Baghdadi’s death, all of which have proven false.
There was growing speculation that he had been killed after not being seen in recent months, but he was reportedly spotted last month.
At the same time, the US government raised the price on his head from $10million to $25m.