( CNN ) His voice , his posture and his threats are menacingly familiar . The black-clad ISIS militant shown in a video demanding a $ 200 million ransom to spare the lives of two Japanese citizens looks and sounds similar to the man who has appeared in at least five previous hostage videos . The knife-wielding masked man with a London accent , nicknamed `` Jihadi John , '' has issued threats and overseen the beheadings of American and British captives . `` You now have 72 hours to pressure your government in making a wise decision , by paying the $ 200 million to save the lives of your citizens , '' the man in the video that appeared Tuesday says in comments addressed to Japanese citizens . `` Otherwise , this knife will become your nightmare . '' Q & A : Harsh realities of kidnappings , ransom . The amount of money is the same as that recently pledged by Japanese Prime Minister Shinzo Abe in humanitarian aid to Middle East countries that are affected by ISIS ' bloody campaign in Iraq and Syria . Japan believes the deadline arrives Friday at 12:50 a.m . ET . And Chief Cabinet Minister Yoshihide Suga said Wednesday the country will do its best to communicate with ISIS through a third-party nation . But mystery and confusion still surround the identity of Jihadi John . U.S. and British officials have said they believe they know who he is , but they have n't disclosed the information publicly . That could be because Western intelligence agencies believe they have more to gain from keeping quiet , says Aki Peritz , a former CIA officer . `` They can put pressure on his family , put pressure on his friends , '' he told CNN . `` Maybe they have a line to him . Maybe they know who his cousins are who are going to Syria who can identify him . However , if you publicly tell everybody who he is , his real identity , then maybe he 'll go to ground and he 'll disappear . '' There had been reports that Jihadi John was injured in a bombing attack by the U.S.-led anti-ISIS coalition . But the video that appeared Tuesday would suggest , if it 's really the same person , that he 's alive and well enough to make a death threat accompanied by a demand for money . His apparent reappearance helps ISIS ' slick propaganda machine , which is used by the extremist group to raise money and recruit followers . `` It shows them resilient -- that they 're able to film this video with these Japanese hostages outside in broad daylight somewhere presumably in Syria , '' said CNN terrorism analyst Paul Cruickshank . Five months and roughly 2,000 airstrikes after ISIS ' video of the killing of U.S. journalist James Foley , why does one of the West 's most prominent tormentors appear to still be at liberty ? U.S. and British military and intelligence officials declined to comment on the matter . Experts say the problem lies in the extreme difficulty of infiltrating commandos into Syria to reach Jihadi John . `` ISIS operates in what we call denied territory , '' said Cedric Leighton , a retired U.S. Air Force colonel . `` And that means by definition , that it 's very hard for our folks to get in there , it 's very hard for them to actually lay eyes on target . '' A mission by U.S. special operations forces in July failed to find Foley and other hostages in Syria . `` The attempt to rescue Mr. Foley is one of the things that has now made the White House very reluctant to act aggressively , '' said Tony Shaffer , a former U.S. intelligence operative , who directed special operations in Iraq and Afghanistan . A senior U.S. administration official , however , said the U.S. government is `` actively pursuing justice '' for the slayings of the hostages . `` The FBI has an open criminal investigation , and as you have seen , we will hold terrorists like this accountable , no matter how long it takes , '' the official said on condition of anonymity . `` For operational security reasons , we are not in a position to detail all of the steps we are undertaking . '' Meanwhile , as ISIS ' deadline draws nearer , the Japanese government has to decide how it will respond to the extremists ' latest life-or-death ultimatum .
Western officials have said they believe they have the identity of ` ` Jihadi militant '' But they may be using it as a way to get closer to him , an ex - CIA officer Mr . Expert : The black - clad militant 's latest appearance shows ISIS ` ` resilient ''