BEIRUT - A man identified as British journalist John Cantlie has purportedly appeared as a captive of Islamic State militants in a video posted by the organization's supporters online.The Islamic State group, which controls territory in Syria and Iraq, has already beheaded two American journalists and one British aid worker in recent weeks in what it said was reprisal for US air strikes against it in Iraq.But in the new roughly three-minute video, the man identified as Cantlie appears in good health and promises to "convey some facts" in a series of "programs," suggesting there would be further installments."Now, I know what you're thinking. You're thinking, 'He's only doing this because he's a prisoner. He's got a gun at his head and he's being forced to do this.' Right?" the man in the video, wearing an orange shirt and closely-cropped hair, says."Well, it's true. I am a prisoner. That I cannot deny. But seeing as I've been abandoned by my government and my fate now lies in the hands of the Islamic State, I have nothing to lose."US President Barack Obama has been trying to build an international coalition to destroy Islamic State, a militant group which has exploited the chaos of Syria and Iraq's conflict to seize swathes of territories in both countries.The United States has already carried out scores of air strikes against the group in Iraq and Obama said in a policy speech he would not hesitate to strike it in Syria as well.In the new video, titled "Lend Me Your Ears, Messages from the British Detainee John Cantlie," the man identified as Cantlie says he was captured by the Islamic State after arriving in Syria in November 2012.He says he worked for newspapers and magazines in Britain including the Sunday Times, the Sun and the Sunday Telegraph."After two disastrous and hugely unpopular wars in Afghanistan and Iraq, why is it that our governments appear so keen to get involved in yet another unwinnable conflict?" the man says in the video.