Possible American Accent Detected in ISIS Horror Video U.S. intel attempting to determine if masked figure has U.S. ties.

 -- U.S. intelligence officials are analyzing facial features and speech patterns of the masked man who spoke in a recent ISIS video to determine who he is, and if he could be one of ISIS’s American recruits, according to a senior U.S. official.

The masked man speaks briefly in the video, which purports to show the gruesome execution of 21 Coptic Christians in Libya, declaring that ISIS’s Libyan affiliate is “on the south of Rome,” an apparent reference to ISIS’s expansion into Libya and the threat it poses to the West.

Professor Erik Thomas, a linguistics expert at North Carolina State University, told ABC News that based on distinctive word pronunciations, “he sounds like an American” with some Arabic influence. Another linguistic expert from another American university, who requested he not be named, said the masked man may be a native Arabic speaker but came to learn American English likely by spending a “significant amount of time” in the U.S.

As in the hunt for the ISIS fighter dubbed “Jihadi John,” U.S. officials are conducting detailed analysis of the clues on the video. In the “Jihadi John” videos, believed to have been shot in Syria, authorities say they have been able to identify that masked figure with a British accent who appeared to murder Western journalists and aid workers. He is believed to be a British citizen, officials say, though he has not been publicly named.

The potential role of an American ISIS recruit – which would not be a first for the terror group -- comes as the White House today began a three-day effort with community leaders to stem the flow of the terror pipeline from the U.S. to the Middle East.

One front on which ISIS has been successful in recruitment, analysts and U.S. officials have said, is on social media. J.M. Berger, terrorism expert and author of a forthcoming book on ISIS, estimates that the group has 30,000 to 40,000 supporters active online every day.

The U.S. State Department has attempted to counter ISIS propaganda by engaging would-be jihadis one-on-one online, sometimes by calling adult ISIS fighters cowards who use women recruits only for sex. Some analysts say the U.S. campaign of insults misses the mark.

“It’s not impacting the people who may be inspired by the ISIS ideology and will carry out attacks on its behalf,” said John Cohen, former Counterterrorism Coordinator at the Department of Homeland Security and current ABC News consultant.