A fourth video message has been released by Isis (also known as Islamic State) militants featuring British photo journalist John Cantlie.
In the video titled Lend Me Your Ears, the 43-year-old says IS 'eagerly awaits' a ground war with America and warns that a clinical offensive where no one "gets their hands dirty" is impossible.
Dressed in an orange jumpsuit, he also addresses the issue of air strikes by Western forces in Iraq in the video which lasts six minutes and 53 seconds.
He says: "One month ago Obama pressed the button on air strikes. Now we have to wonder how long his policy of no boots on the ground has left to live. As for IS, they eagerly await to see those boots."
Cantlie, who Isis militants have threatened to kill next, speaks of the recent beheadings of IS hostages David Haines, James Foley and Steven Sotloff, appearing to read from a script.
"Now you want to use these deaths to fan the flames of war. If this is the case I deeply resent it Prime Minister. Thanks a lot."
An article allegedly written by Mr Cantlie has also appeared online in an IS magazine titled "The real story behind my videos" in which it is claimed he wrote the scripts for the videos himself.
In the article he describes seeing previous hostages before him being taken to the death.
He says: "I've had to watch as James (Foley), Steven Sotloff, David Haines and Alan Henning, walked out of the door, one every two weeks since August 18, never to return, knowing they were going to be killed and going to their deaths.
"Four of my cellmates have already been executed by the Islamic State in the most visceral way possible after the British and American governments apparently made a joint decision not to discuss terms for our release with our captors. And now, unless something changes very quickly and very radically, I await my turn."
A Foreign and Commonwealth Office spokesman said: "We are aware of the video and article and are investigating their contents."
Cantlie was apparently captured in northern Syria in 2012, when he had been working as an independent photojournalist.
Earlier this month his father made an emotional appeal for his release.