A convicted counterfeiter who had a grudge against the government was arrested on Thursday for plotting with undercover U.S. agents to blow up the building housing federal offices in Chicago, prosecutors said. Gale Nettles, 66, told a fellow inmate of his desire to use a fertilizer truck bomb to blow up the Dirksen federal building, authorities said. The inmate told authorities, and undercover FBI agents and other informants contacted Nettles after he was released from prison last year. "The only people he dealt with were FBI agents and informants ... this had nothing to do with any terrorist group," U.S. Attorney Patrick Fitzgerald told a news conference in the building Nettles was suspected of targeting. "Today's action is not related to the nation's current terrorism threat level. Nettles was always acting alone and had no connections to any terrorist organization," Fitzgerald said. He said the Dirksen building, a glass and steel skyscraper that houses courtrooms as well as the offices of the FBI and federal prosecutors, was never in jeopardy. --MORE 2339 Local Time 2039 GMT