CHICAGO (Reuters) - Prosecutors preparing to try a Pakistani-born Chicago businessman on charges he aided the 2008 Mumbai attackers invoked a secrecy law on Wednesday to control evidence disclosures in the case. Defendant Tahawwur Rana looked on during a federal court hearing where Patrick Fitzgerald, the US Attorney in Chicago, and other prosecutors asked the judge for a private hearing to lay out the governments classified evidence. The judge set the hearing for March 29. The law in question, the Classified Information Procedures Act, seeks to balance a defendants rights against the governments desire to protect secrets and its information-gathering sources and methods. Rana, 49, is charged along with American David Headley with allegedly providing support to the Mumbai attackers. The FBI made tape-recordings of Headley and Rana purportedly discussing the Mumbai attack and a plot to attack a Danish newspaper, according to court papers. Ranas Attorney, Patrick Blegen, met with Fitzgerald and a representative of the US government privately both inside and outside the courtroom. Blegen said little about the evidence issue afterward, but he has filed court papers demanding the government provide specifics of how Rana supported Headley and the Mumbai attackers. Prosecutors have said Rana was deeply involved, using his immigration business to provide cover for Headleys travels.