NEW YORK (AP) - Disgraced radio host Don Imus will sue CBS Radio for the huge portion of his $40 million contract that was left unpaid after he was fired for racist and sexist comments, his attorney said Thursday.

Martin Garbus, a First Amendment attorney, said the case involved simple contract law rather than any constitutional issues.

Imus, 66, was barely three months into the five-year deal with CBS when he was dismissed April 12 after describing the Rutgers women's basketball team as "nappy-headed hos" on his nationally syndicated radio program.

Garbus cited a contract clause where CBS acknowledged that Imus' services were "unique, extraordinary, irreverent, intellectual, topical, controversial." The clause said Imus's programming was "desired by company and ... consistent with company rules and policy," according to Garbus.

Garbus said he expects to file the state lawsuit in Manhattan by next week.

CBS Radio spokeswoman Karen Mateo did not return a call seeking comment.

Garbus' past clients include comedian Lenny Bruce, the rap group Public Enemy and filmmaker Spike Lee.