NEW YORK - US prosecutors on Friday sought to unseal the to-date secret criminal case of an Islamic State defector after NBC News broadcast an interview with the New York man in which he spoke out against the militant Islamist group.The 27-year-old man had been cooperating in investigations and had explored speaking publicly against the militant group "for some time" before agreeing to the NBC interview broadcast Thursday, prosecutors said in a letter filed in federal court in Brooklyn, New York.Unsealing the case could allow the US Justice Department to make public details of why the man turned against Islamic State at a time when the government is trying to combat the group's online propaganda.The man, identified only as "Mo," pleaded guilty under seal in November 2014 to charges including that he provided material support to Islamic State, the letter said.US authorities arranged the NBC interview after learning the network was preparing a story on Mo, who NBC said attended Columbia University, prosecutors said in the letter."Islamic State is not bringing Islam to the world," Mo said during the interview. "And people need to know that."A spokeswoman for Brooklyn US Attorney Robert Capers declined comment. Mo's lawyer did not respond to requests for comment. NBC had no immediate comment. Mo is one of more than 85 people since 2014 to face US charges over crimes related to Islamic State, which controls territory in Syria and Iraq and has claimed responsibility for attacks in Paris in November that killed 130 people.Prosecutors said in June 2014, Mo travelled from Brooklyn to Syria, where he enlisted with Islamic State. Once there, they said, he received military training and served as a sentry at one of its headquarters and in various administrative positions.But Mo became "disillusioned," prosecutors said. During the NBC interview, Mo said "towards the end as things were getting more and more serious, I did see severed heads placed on spiked poles."In November 2014, Mo escaped across the border into Turkey and found his way to a US State Department outpost, prosecutors said. Once back in the United States, he was arrested and began cooperating.