An American man pleaded guilty after he and a Pakistani living illegally in the United States were charged with conspiring to join the Taliban and fight against US forces, federal prosecutors announced Tuesday. US Attorney Donald J. DeGabrielle Jr. said a four-count indictment charges Kobie Diallo Williams, also known as Abdul Kabir, and Adnan Babar Mirza with conspiracy. Mirza, a 29-year-old Pakistani who overstayed a student visa, also is charged with three counts of violating federal firearms laws. Williams, 33, a US citizen living in Houston and attending the University of Houston-Downtown, surrendered Tuesday to members of the FBI's Joint Terrorism Task Force and pleaded guilty in US. District Court to the conspiracy charge. Mirza was already in custody on immigration violations.